There are arguments to support both views, I suppose. If you allow false names people can disclose unflattering but honest facts about the place they work without the risk of their employer getting upset. On the other hand, if people had to use their real names they may be less inclined to make stupid comments - or even to be unpleasant towards other members of the site.
The decision is partly down to what sort of site do we want ? If it's a very informal, let's have a joke and a chat sort of site, then silly names don't matter.
If it's a site where we are trying to promote the idea that we're all very professional people who take our job - and our responsibilities - seriously, then the less frivolous comments and exchanges should be discouraged and using real names would (probably) achieve that.
But then you could make similar comments about the "silly" pictures we identify ourselves with ! I doubt if a blue frog is in line with a serious, professional image ! :p
