Ask Pmarca

Say I come up with an idea, do my market research, find no one has done it yet, and get to work on implementation. In the meantime, someone unveils a site that does the same thing. Oops--race condition! What should I do? This actually happened to some friends of mine. (They gave up.)

A variant: say I come up with a good idea and find it's *already* been done? Should I try to do it better (a la Facebook), or should I just move on to the next idea?