Social networking site Facebook is considering a takeover offer from Yahoo after already turning down Microsoft and Viacom. 

Facebook founder Mark Zuckerberg has reportedly said that he would not sell the site for less than $2bn, but Yahoo is believed to offering the 'bargain' price of $1bn.

Yahoo has already shown its keenness to break into the social networking market, having just announced a partnership with user-driven video website CurrentTV. 

According to figures from analyst ComScore Networks, 76 per cent of the entire internet audience visit Yahoo websites, whereas only nine per cent visit Facebook. 

However, just over a third of Facebook's visitors are aged between 18 and 24, while Yahoo's biggest audience is the 39 per cent of its users aged 35 to 54.

Facebook had been primarily aimed at US college students, but has recently opened its doors to any user. 

YouTube has launched a similar service aimed specifically at college students in a bid to encroach on Facebook's market.

"I would never say that at no point in the future would we go public or become part of a larger company. But it is not our priority," Zuckerberg told The Wall Street Journal.