Yahoo's My Web, launched in beta form in April, adds a new twist to the web search theme. My Web saves your browser history online, letting you easily search or revisit web pages. It builds on the functionality of the Yahoo toolbar, and can save the entire page, rather than just the URL, just in case the content changes or goes offline.

But there are worrying aspects to My Web and the Yahoo toolbar, just as there are with the equally natty toolbars from Google and A9.com, part of Amazon. It is all to do with the three unavoidable issues of the internet: privacy, security and identity.

Each of these browser add-ons sends a record of every URL you visit to the vendor's servers, and when you install, you agree to allow this information to be used for various purposes, including targeted advertising.

In the internet era, the links someone makes from their web browser reveal a huge amount of both business and personal information. Respected firms such as Yahoo, Google and Amazon are anxious to emphasise they will not misuse the information. And it is quite possible to deliver customised advertising without ever making the link between a person and their browser history.

On the other hand, the mere existence of all this data is a cause for concern. I imagine many users install and use these toolbars without reading the privacy policies and terms of use, but if they do seek them out they will not find them reassuring. Here is an example from A9.com:

"A9.com's toolbar service collects and stores full uniform resource locators (URLs) for every web page that you view while using the A9.com toolbar service. These URLs sometimes include personally identifiable information... A9.com is able to correlate information it collects with personally identifiable information that Amazon.com has, and Amazon.com has access to information collected by A9.com."

Frankly, I doubt anyone reading and understanding such an agreement would want to install this particular toolbar, but individuals can make their own informed decisions. The real worry is that users are typically not given clear information. In Yahoo's case, to install the toolbar you have to pass a licence agreement displayed in a small scrolling window. If you read it, you will find it refers to a further terms of service agreement which is only available online. This sort of obfuscation is unacceptable.

When you take out a loan, you want to see the annual percentage rate (APR). Security and privacy deserve similar prominence when you sign up for internet services.

Some are better than others. Google's toolbar does allow you to disable the reporting of every URL you visit, at the price of losing certain features, while Microsoft's MSN Toolbars appear to be better behaved from a privacy perspective.

Unfortunately, it is difficult to work out which add-ons are safe, and the easiest solution for firms is to enforce use of an unadorned web browser. It is a shame, because there is real value in context-driven searches as well as the ability to search intelligently through your browser history.