This is way too dramatic and unprofessional for my tastes (Facebook chat logs? followed up by a generalization about the 8.3 million strong population of NY based on experiences with one guy? a little growing up is in order.)

I'm sure this can be debated and I could be wrong, but I don't feel that ideas are worth fighting over. If code is stolen, that's not cool. You can build two codebases based on the same idea and they will be valuable in different ways. If someone takes the time to follow through on implementing "your idea", they still most likely worked hard to get it done and deserve credit for that.

The best way to deal with this is to compete. Write a better app. Ideas are cheap.