People keep telling me that a trait of entrepreneurs is focus. But what if an entrepreneur can create and realize 2 or 3 ideas at the same time? Why wait to finish/fail 1 and then start the other?
I'm with Jeff. If you're not quite sure which idea to pursue filter it by 1) passion, 2) by the biggest problem that needs solving, 3) market timing.
Find a super fast way to test the above three, then choose. Once you start, it is practically impossible to "run" more than one idea as a startup.