Solutions for the pollution of a social network?

LinkedIn is a social network for professionals. It’s all about who you know, and who you have worked with. The basic idea seems to be that recording all that information will result in new business opportunities, as well as referrals to jobs et cetera. When someone who claims to have worked for your company joins LinkedIn, you get email asking you if you know them.

So, what do you do when you look in the company address book, and it’s quite clear that they don’t work for your company? There doesn’t seem to be any way in the UI to point out that someone is lying. How annoying.