LinkedIn users are being urged to contact the company to complain after it was revealed that a change in privacy policy now allows third-party advertisers to harvest users' profile information and pictures in their ads by default.

Blogger Steve Woodruff appears to have been the first to notice the changes to LinkedIn's Terms of Use, which force users to manually untick a box in the Manage Social Advertising section of their privacy controls.

Paul Ducklin, Sophos head of technology in Asia Pacific, suggested that LinkedIn is making the same mistake as Facebook with its much-maligned decision to make face recognition functionality opt-out.

"Crudely put, LinkedIn will mine your usage habits to determine what products and services you're interested in, and then use your name and photo in what amounts to an endorsement for those products and services when they're advertised to other users," he said.

"This feature is opt-out, even though it reduces your privacy and infers your goodwill, and wasn't part of LinkedIn's service when many current users signed up."

Ducklin urged LinkedIn subscribers to complain via the abuse@linkedin.com email address, as well as turning off the option in question.

LinkedIn has been criticised in the past for providing cyber criminals with a treasure trove of personal information with which to launch phishing and other socially engineered attacks.

Users will now be hoping that today's news is not an indication that the site will make privacy mistakes more commonly associated with Facebook.

In response, LinkedIn argued that it flagged up the changes to its Terms of Use several times when they were introduced in June, explaining how users could opt-out.

"In addition, as LinkedIn does with all changes to its User Agreement and Privacy Policy, we notified our members of the changes to these documents via a banner displayed to when they logged in to their account," it added.

"This banner contained a link to the new documents, including a summary of the changes and links from which our members could easily access their account settings. "

So, the tech bubble continues to inflate. Groupon, an online deals web site with over 80 million email subscribers, has launched its initial public offering (IPO) in an attempt to raise up to $750m.

As we wrote recently, LinkedIn's flotation and subsequent rocketing on the New York Stock Exchange seemed oddly reminiscent of the tech bubble of the late 1990s, although financials analysts argue that there is more intrinsic value in the companies going public this time.

Nevertheless, the figures being thrown around are somewhat ludicrous. Groupon
posted a net loss of $102m for the first quarter of 2011 and has a deficit of $522m, yet the company has already turned down a whopping $6bn offer from Google.

Groupon is clearly confident, so much so that, in a twist on the usual stuffy IPO system, chief executive Andrew Mason went all wacky and Google by writing a letter almost daring investors to get onboard, promising that the company would not be prudent in its dealings.

"We spend a lot of money acquiring new subscribers because we can measure the return and believe in the long-term value of the marketplace. In the past, we've made investments in growth that turned a healthy forecasted quarterly profit into a sizeable loss," he said.

"When we see opportunities to invest in long-term growth, expect that we will pursue them regardless of certain short-term consequences."

Mason added, with a flourish, that the industry is breaking new ground and will throw up moments of great despair, but also joy.

"As with any business in a 30-month-old industry, the path to success will have twists and turns, moments of brilliance and other moments of sheer stupidity. Knowing that this will at times be a bumpy ride, we thank you for considering joining us," he said.

There are echoes here of the letter written by Google founders Larry Page and Sergey Brin, which warned investors that the company was about risk taking and rewards for employees, not securing stable quarterly balance sheets.

"Expect us to add benefits rather than pare them down. We will optimise for the long term rather than trying to produce smooth earnings for each quarter. We will support high-risk, high-reward projects and manage our portfolio of projects," they said.

Google's approach certainly worked. The question now is how Groupon performs when it hits the markets, and whether it can last. And you can be damn sure the folks at Twitter and Facebook will be watching like hawks.

There's been a lot of speculation about numerous internet behemoths going public on the stock market, so all eyes were on LinkedIn's share ticker on Thursday as the firm hit the New York Stock Exchange.

And all eyes were soon rolling upwards as LinkedIn's share price doubled from $45 to $90.49 within four minutes of the opening bell, and had hit an all-time high (admittedly in one day of trading) of a whopping $115.09 per share by 11:48am.

No doubt those who stuck a wedge of cash in the business version of Facebook would have been patting themselves heartily on the back as fortunes were made - on a company that turned a profit of just $15m in 2010.

How LinkedIn performs today will be of interest; was day one nothing more than frenzy based on novelty, or do the financial whizz kids of Wall Street see something in LinkedIn that appeals to their monetary senses?

The firm's performance in the coming months could well be the reason that other giants of the social media world, such as Facebook, Twitter, Groupon and gaming firm Zynga, which owns the bizarrely popular Farmville, go public. Or not.

The smart money would suggest it'd be good to get some stock in these companies before the trading bell rings if they float based on LinkedIn's early rises. But others will see the money involved as further signs that we're in a second tech bubble.

One public offering is hardly a bubble in itself, but the money involved is amazing; LinkedIn's paltry $15m profit was its first in four years, while sites like Facebook are valued in the countless billions owing to huge numbers of loyal subscribers.

However, both rely primarily on the age-old cash cow of advertising for the majority of their revenues, alongside more capricious income streams such as Facebook's developer fees or Twitter streams in Google and Bing searches.

Irrespective of the financial unknowns, executives and shareholders in LinkedIn no doubt spent a pleasant night smoking cigars lit by $50 bills as their investments made them more money in one hour and 48 minutes than most will earn in a year.

More often than not it appears the only time Twitter hits the news is when a celebrity says something stupid or the site crashes, as witnessed on Wednesday.

However, it would be foolish to think that sites like Twitter, or indeed Facebook and LinkedIn, are nothing more than online water coolers around which bored office drones flock, as several announcements from major tech vendors this week have underlined.

At the annual SAS Global Forum event in Las Vegas attended by V3.co.uk there has been a huge focus on social media and the need for businesses to make sure they stay on top of the deluge of data being created on sites like Twitter and Facebook.

As such, the vendor announced the forthcoming availability of a new Conversation Connector tool for its Social Network Analysis (SNA) platform that lets users monitor Twitter for keywords and phrases, and crucially their sentiment, so staff can manage and proactively deal with any complaints that arise online.

Users can also track which customers have the biggest influence when they say something, so they can be sure they are watching to see if a key person is mentioning their brand, particularly with any negative connotations.

There is of course a privacy issue here, at least a perceived one, as many Twitter users may be somewhat perturbed if they realised a retailer was watching and reacting to their every tweet, but if doing so leads to better customer satisfaction, many may find their initial abhorrence wane.

SAS did admit that it perhaps needs to get some of its early adopter customers to talk up their experiences with SNA to help increase its penetration from a mere handful of customers at present, and said most are unwilling to do so because they fear a potential backlash from customers.

Yet SAS clearly feels this is an area worth pursuing and the buzz in Las Vegas is further augmented by the wealth of news coming from California-based SugarCRM which has made a slew of annoucements relating to social media.

The company's updated Sugar 6 product will include a tool called Sugar Activity Streams to help users integrate Twitter and Facebook feeds into their CRM management tool and help users track conversations and reply to comments and posts on key social sites.

It certainly seems as if the winners in the business world will be the ones that don't just track their brand's reputation online but get their hands dirty and start engaging with customers quickly, efficiently and proactively.