The Geo and citizen journalism angle I think makes these guys really unique. Also, its just really really fast and easy to start streaming. When it is that easy, you start living streaming everything.
That's what I like, even they originally pitched as a way to stream for conferences (including a very weirdly streamed TEDx conference), what they've built is the best streaming tool out there for one to many.
David, Tyler, Paul, and Vu have built something awesome that allows anyone to create. I already know people who can't stop using it. I just wonder what happens once it explodes...
The geographic aspect of Tapin is one of the things that I like the most. It makes finding video relevant to me so much easier, and it's something I really haven't seen in other sharing contexts. I'm pretty excited for Tapin.tv