Somehow, I find myself trusting Diigo more than Facebook, although you can connect to Facebook via Diigo. What's also present is the potential for "Diigo-spam." Ok, I've spammed everyone in my addressbook. I can't remember the last time I did it, but I hope that if you received an email via Diigo from me, you'll jump in and give this a try. If you don't want to, hit delete. Do I think Diigo is that powerful a tool? Well, yes. It offers something Delicious doesn't--groups, and a base of operations that interfaces with other tools. If I could share information using Diigo, ohmygosh, one ring to rule them all. One of the other aspects of Diigo I liked was that the Diigo crew is hopping to improve things. Importing bookmarks from Delicious API wasn't working well (i had to try 3-4 times), so they came up with an alternative way to accomplish the import. Dean Shareski complained about the interface, and they re-did the user interface. There's also talk of creating an education (student) friendly Diigo....

Easy group subscription - I wish there was a URL I could share with people. They click on it, and bam, if they have a Diigo account, they're subscribed. If they lack an account, it walks them through the process then makes sure to hook them up with the group. I just don't see how to do it easily now.