SocialStartups.com

Here’s my Amazon profile page, annotated using Fleck.
First off, notice that you didn’t have to sign in to see it. Secondly, I’ll note that I also didn’t have to sign in to make it. No registration = bliss (and adoption!)

Third, notice that the notes are wiki style. Anyone can edit them. Very handy for collaboration, although I don’t see any versioning controls — that’s a key feature for wikis.

Key question: How will they make money? Definitely something for them to think about. It’s always easier to negotiate an acquisition if you’ve got a real business plan to fall back on.