I see that Matt has opened up WordPress.com for signups without invites. So you no longer need an invite or a copy of Flock to signup for a WordPress.com blog
The service has been scaling very well since we got the problems from the move worked out.
This is very exciting news. I think there will be some great things to come out of this project. Especially the community aspects.
I also noticed that Google’s Gmail has removed the “invitation” block from the logged in screens. Though there isn’t a general “sign up here” notice on their home page. However like using Flock to get into WordPress.com, there has been a non-invitation route in to gmail for a while; you can sign up to Gmail via SMS.