It must be horrible to see someone else ripping off your work like that. I mean Pinspire is almost identical to Pinterest. The question is what do you do? do you ignore them and try to focus on your product without letting anger affect your creativity and the initial flow of ideas or do you try to compete with them?
I think you've put your finger on it: the biggest danger of people copying you is not the competition, but that anger at them will distract you.
As competitors they're not as dangerous as they seem. Copying someone can tell you what to do, but it can't tell you why you're doing it, and you're probably not going to do something well if you don't know why you're doing it.
