Facebook and LinkedIn are the latest players in social networking. Which you choose depends on whether you prefer to talk to managing directors or throw cakes at them.

Now, that’s what I call investigative journalism. I got to spend an entire working day on Facebook, the latest time-wasting craze sweeping the internet.

If you’ve been on the moon for the past month, you may not know that this is fast becoming one of the most popular online networking communities. Much like MySpace, you make a profile and sign up some friends. Then you can chat and generally muck about on discussion boards, like the Anti-Norman Foster group, illustrated on the site by an erotic gherkin flanked by two Millennium Domes.

I can’t imagine Richard Rogers is too happy that one of his buildings has ended up as the veg to Foster’s meat. He’d probably prefer to spend time on LinkedIn, the more grown-up rival to the student-dominated Facebook.

LinkedIn’s aimed at serious-minded professionals like you and I. There’s less frivolity, no chance of a virtual foodfight or any “superpoking”, and invitations to join are much harder to come by – reflected in people’s lists of contacts, which include directors and vice-presidents.

On Facebook, in contrast, “friends” are not defined by such tedious technicalities as their jobs, but rather by how they are feeling on a particular day.

And, predictably, web stats reveal that the growth of LinkedIn has plateaued, while Facebook’s has rocketed in recent weeks. Clearly, people would rather throw virtual cakes at online contacts than build professional relationships with them.