Not so sure that pointless is a valid criticism - nearly pointless I would allow you to use...

After a brief flirtation with facebook I have come to the conclusion that it does have its uses. Keeping in touch with people you wouldn't otherwise bother to, and organising and publicising events, being the main ones for me. But then I'm useless at keeping in touch normally...

As for the others I have no comment to make, other than I probably won't be joining them...