I don't mean to belittle I Move You in making this comment, but would companies like this exist (as companies, not side projects) if they didn't have programs like ycombinator to catapult them into the spotlight? It seems to me that without the adrenaline shot that is ycombinator + techcrunch, one would have an incredibly difficult time successfully bootstrapping an idea like this that depends so much on the network effect.
Interesting concept. I think we're going to see gaming mechanics applied to a lot of social activities in the near future. This is a lot more appealing to me than checking in or something. Or at least it would be if I could do 50 situps and survive it.
This is such a great idea - I find that it's very easy to rationalize myself out of the goals I set, but as soon as another person is involved it makes it 10x harder to back out... it's sort of like the inverse of the Milgram experiment.
Why I think they are onto sthg: think of it as "behavior programming" (like Mydunktank we had put a short post on this <a href="http://blog.quantter.com/post/874726318/getupanmove-me-mydunktank-com" rel="nofollow">http://blog.quantter.com/post/874726318/getupanmove-me-mydun...</a>) It seems simple and stupid and may be overlooked as such but this what great ideas are made of. As pg said <a href="http://www.paulgraham.com/organic.html" rel="nofollow">http://www.paulgraham.com/organic.html</a>: "if what you produce initially is something other people dismiss as a toy. In fact, that's a good sign."
Looks pretty nice. Small bug that I found while wanting to show the website to a friend: when you want to send a challenge by email and it asks you to login.. I get a 404 after email/password creation.