I have a facebook group and I assumed the links were nofollow, but google has it listed in my webmaster tools as a link. It is a pr 5
They are nofollow - google does list nofollow links in webmaster tools - yahoo answers links show up there too
But now some search engine could indexed the no follow links,so it is useful,and i think it could increase the traffic to your site.
Yes, they are nofollow. Actually, you can easily check with using the Firefox add-on "Search Status" for checking yourself.