Ideas are Worth Nothing
kevendones.posterous.com
kevendones.posterous.com
For example, when HuddleChat, a knock-off of 37 Signal's Campfire, was released, there was a bit of a frenzy. Someone copied all the ideas in the app, and apparently those ideas were worth something.
Simple, high-level, abstract ideas may have lower value; detailed ideas, ideas about execution and presentation have more value. At some point, they are worth protecting.