I hate the formality of contracts, but is there any good procedure early on for avoiding this in the future? It seems every billion dollar company has a "secret" cofounder that shows up when the money does. I know I've definitely shared ideas and even code with friends, long before my startup became an incorporated startup.
I'd feel silly and presumptuous if I started handing out contracts, of course. Maybe something more along the lines of the YC handshake protocol, as opposed to a formal contract? Does it legally matter if you say "Hey, just wanted to acknowledge we talked a lot about this, and wanted to make sure you were okay with [terms]" and record the response?