A way to test the market or get social proof that there is a market for this. Checkout how buffer did it - http://blog.bufferapp.com/idea-to-paying-customers-in-7-week...

You need 2 things: Landing page to describe product/etc and a community to support say yes/no

BTW did you see http://www.startuprocketlauncher.com/ on HN today as well?

Awesome first link.

For the second, no I didn't see that until now. Hmmm. I wonder if that's somebody being clever to prove a point of how easy ideas are to steal? If so, kudos for the irony :)

Sadly, luck is as important as good execution.