Or I had an idea where people could buy shares in bitcoin run companies (Things like Mining Pools, BitCoin Service Offerers and more..)
Sounds like http://glbse.com/
- though that's in beta it's appears to be moving quite quickly to something quite useful. That doesn't mean that they can't be competition. They "nefario" just have a giant head start on you.
Seriously though, ideas are worthless without execution. Next great idea you have get coding and go for it! Recruit others if the idea is too big for just you.