I have a few Gmail invites going spare, the first six people to private message me will get one each.

I already have a couple of Yahoo addresses, so I don't think I need another email address!!

How come Gmail is only open to invites? Is it to stop spam?

I'm not sure but I think one of the reasons they choose this method was to stop a sign up frenzy when they launched.

Also by going down the invitation route they can minimise the strain on their servers and iron out any initial problems before going completely public.