Adam Doppelt (co-creator) here. Feel free to chime in with technical questions and I will attempt to answer them. That's half the fun of a side project!
Given your background, have you considered building a similar "duel" for restaurants? Mostly I'm curious how the restaurant duel numbers would compare to Urban Spoon's rankings. (There is the problem that not all users will have been to all restaurants, so maybe restrict to a small popular subset in each geography?)
Resto duel is an interesting idea. Ethan (from Urbanspoon) actually mocked this up at one point but we thought it was kinda lame. The results just weren't that compelling, sadly.
The first system to fall over was our message-queue that talks to LinkedIn for logins and refreshes. I had to spin up a separate machine at Rackspace just to help logins along. Hopefully that'll hold things steady for a bit.