First of all NoSQL isn't really that hard and the performance gains are indisputable. For a bootstrapped startup nosql makes total sense b/c you get much more

First of all NoSQL isn't really that hard and the performance gains are indisputable. For a bootstrapped startup nosql makes total sense b/c you get much more performance for your dollar. Sure you can go the vanilla PHP/MySql or Django/Postgres route if you want to build your prototype but you will be in a bad position if your system can't scale with demand. I would build the prototype first in your favorite framework/setup.. If it has market potential after some initial private beta testing I'd definitely go the nosql route.