Unless you live in a world where patent extortion exists (darn it, isn't this true?) your ideas are worth nothing. In a Tech Startup world what matters is execution!
There are a lot of "ideaman" that claim company A stole their idea. Some even go to the extent of suing company A. It might even be true that they stole it from you, but more likely you (or your startup) were not well equipped to execute on that idea, or were too slow, or simply tried and failed. And, now you want credit for what? For a thought?
Sure, from an ethics perspective you shouldn't steal other's people idea, but if that was a black-on-white statement, the world would not evolve. I didn't create the idea of "blog", but I certainly added it to Sampa. I didn't create the idea of online photo albums, or menus, or headers, or a lot of the things I put on the product. Am I stealing ideas?
A friend of mine that went to college with me had a philosophy that there is absolutely no new ideas to humankind on its entire history. Everything is an evolution of something that came before it. He used to say people can never say "I created X", because they didn't, he suggested that what people did was "connect Y and Z and got X".
Now, stop talking (or asking for an NDA) about your idea and just do it.