Finding way to recruit developers

Looking to build out a list of developers to contact for surveys, studies which would require thousands of participants. It's been a challenge, though, despite being in Silicon Valley. Ideally we'd want nationwide, but even locally it's hard to find them never mind incentive them.

Has anyone recruited developers? Any advice on where to find them and develop your user list? Intercepts haven't worked that well. I'm considering just going boots on the ground and putting up flyers, but realistically I'll get maybe 100 out of that.

What am I not thinking of?