Tech blog (David Gelles): If Silicon Valley technology companies go through something like the stages of life, then Facebook is in its adolescence - growing quickly, and struggling to find its identity.

That it is rapidly bulking up is no longer in question. The latest figures from comScore show Facebook to be the fourth-largest site in the world, with a 340m unique visitors, trailing only the sites of Google, Microsoft and Yahoo. Facebook has added 208m visitors in the past year, a 157 per cent growth rate that has allowed it to surpass MySpace, Amazon and Wikipedia.