Facebook Graph Search 'will threaten Google+'

However, analysts warn that without increased activity the usefulness of the new search feature could be limited.

Facebook announced Graph Search at an event in California last night. The search tool is designed to link up the vast store of information in Facebook's database, making it possible for members to search for friends based on their interests or even for friends of friends.

Demonstrating the feature last night, Mark Zuckerberg gave the example of a recent gathering at his home to which he invited friends based on the search "who are my friends in Palo Alto who like Game of Thrones", the popular fantasy drama.

"Facebook's worst nightmare is a static social graph; if users aren't adding very many new friends or connections, then their personal network becomes less and less active over time," says Forrester's Nate Elliott. "Terrifyingly for Facebook, that threat is very real: We haven't seen significant growth in the average number of friends per user recently."

Elliott adds: "Graph search seems designed to encourage users to add more friends more quickly. If it means users' personal networks change more frequently, and become more active, then that keeps them coming back to the site - which is vital to Facebook's success."

Zuckerberg said the new feature had been in development for more than a year and was so complex that he initially believed it couldn't be done. He said that he did not believe people would use Graph Search instead of a traditional search engine such as Google.

However, some analysts suggest the new feature will threaten at least part of Google's business. Danish Bagadia, of MPG Media Contacts says: "Facebook is not trying to beat Google in search engine offering, Facebook wants users to spend more time on its platform. Facebook is facilitating this through adding number of features within its ecosystem. This is exactly what Google is trying to achieve through Google plus."

One problem Facebook could face is a lack of up-to-date information. Mark Zuckerberg can only find friends who like Game of Thrones, for example, if those friends have decided to 'Like' Game of Thrones on Facebook. Equally, someone who clicked 'Like' on a page a long time ago might have changed their mind but not gone back to remove the Like from the page.

"It's only as reliable and useful as the tags people use. Most of us don't regularly update our favourite films lists on Facebook, for example," says Ernest Doku, of uSwitch. "Because the extent of Graph Search is limited by security settings, it will probably result in users finding that responses to their queries are not as useful as hoped. This is particularly true for the clued-up younger Facebook generation, many of whom have tight security settings on their profiles."