Sometimes a startup idea is already stuck in the mind of a potential investor. I think pretty much any VC is convinced that ultimately mobile payments or social friend-to-friend shopping recommendations could be huge businesses. The bottle neck is: how to make it work. When you pitch your startup idea in one of these fields, you will be welcomed by a healthy dose of cynicism.  Do not waste your time on preaching to the converted, but have your pitch target the bottle neck in the mind of the investor.