Controversial digital marketing firm uSocial has begun to offer businesses with a presence on Facebook the opportunity to amass more 'friends' on the social networking site.

The company received a great deal of bad publicity when it offered a service selling Twitter followers to businesses, but said that it is able to accurately target Facebook users according to interest group, industry or geographic location.

This allows uSocial to choose the best possible selection of 'friends' and 'fans' to deliver to its subscribers for them to approach via Facebook, the firm said.

"Facebook is an extremely effective marketing tool, as anyone with a large number of targeted friends or fans can attest to," said uSocial chief executive Leon Hill. "The only problem is that it can be extremely difficult to achieve such a following, which is where we come in."

USocial is selling Facebook 'friends' and 'fans' in increments of 1,000, starting at $177.30 (£108.50) for 1,000 names and going up to $654.30 (£400.50) for 5,000 names.

Andrew Yates, chief executive at market surveillance firm Artesian Solutions, argued that the uSocial service shows that businesses are looking at ever more innovative ways to target their key audience.

"Even social networking sites, designed initially to keep up with friends, are becoming more and more business oriented because companies are discovering that the web allows them to pinpoint the exact information they need in order to target certain groups with very little effort," he said.

However, digital marketing firm eConsultancy warned that businesses could fall into a trap if they think that acquiring as many 'friends' as possible will improve their marketing efforts.

"The return on investment in buying 'friends' is hard to spot. Social media is, well, social. Your friends are only as valuable and useful as your interactions with them," said the company in a blog post.

"It may look good to have 20,000 'friends' on Facebook but, if you didn't acquire them by legitimate means, they're not real customers or potential customers. And if you're not engaging with them, they're worthless."