I think any sort of "instant group" website would be a hit right now. I imagine you're outlining the ability to create a SubReddit, and have only specific peop

I think any sort of "instant group" website would be a hit right now. I imagine you're outlining the ability to create a SubReddit, and have only specific people able to participate in it. I think it's a great idea. However, the most crucial ingredient would be an absolute minimal barrier to entry. Don't make me provide and verify an e-mail address, or any of that junk. Just make an obscure URL for each group, and those that get the URL can participate, and/or have a password to enter the group. As wccrawford pointed out, it's more of an add-on to a social network. What's important is the group, not the links per se. So, while bookmarks (and maybe up/down voting) would be important, so would sharing other things, like contact info, files, conversation (forums), etc. Bookmarks and conversation would be the bare minimum.