tribe already has the "review" feature (which unfortunately, I rarely ever see being used, since it doesn't show up on my homepage when I'm logged in.) What about making available a bookmark API that can be placed on websites? Just click the button and post a review and your homepage could notify you if somebody has posted a review of the same site.

The problem with so many social bookmarking sites is that they aren't integrated with great social sites-- this would be different, tribe is already a great social site.

The key to moving tribe forward is to increase its connectivity to the rest of the internet.