I particularly like this case study of the BlockChalk angel round on the Venture Hacks blog. For those who aren't going to click thru and read the whole thing, here's a quick summary.
Joshua Schachter had already committed to invest in the BlockChalk angel round and he suggested they use AngelList to fill out the round. That resulted in commitments from Mitch Kapor, Thomas McInerney, and Josh Stylman. But then Josh Stylman introduced BlockChalk to Chris Dixon and Eric Paley who joined the round. And then with the strength of that syndicate in place, AngelList added Satya Patel, Michael Dearing, and David Liu to finish off the round.
What this shows is that the old model of angel deals is alive and well. Angels love to share deals with each other. It is how angel rounds come together. But AngelList adds at least two things to the mix. First, it adds a place where the deals can come together online. And second it adds people to the mix that would not be part of the offline deal sharing networks that already exist.
I am on AngelList. I see all the deals come together. I don't personally invest in angel deals in the web/tech space because of potential conflict with USV down the road. But even so, I find it immensely useful to see what companies are getting traction in the angel market. It's part of my radar/early warning system. And it is entirely possible that we will decide that USV needs to participate in an angel round that is coming together on AngelList, although that has not yet happened.