Thanks!  If I understand your question correctly, you're correct.  I'm sure there's large groups of bitcoin users that I'm missing by only posting my survey on bitcointalk and /r/bitcoin, which are my main sites of research.  I'll be supplementing my findings from the survey with interviews, hanging out in forms, reading blogs, and hopefully attending some bitcoin events IRL. While I'll really only be able to make claims about the communities of bitcointalk and /r/bitcoin, my focus is on the community aspect of bitcoin, and as far as I am aware this and /r/bitcoin are two of the largest, if not the largest, bitcoin communities online.

If you meant responder bias in terms of people not answering questions entirely truthfully in an attempt to make the researcher happy, I think the same answer more or less applies.  By sticking around here and talking with a number of people, I should get a good feel for the community.

I am also taking great care to protect the anonymity of my participants and am trying to very transparent about what I am doing to protect people's privacy.  So I hope that helps people feel more comfortable with talking to me.

Does this answer your question or did I misunderstand you?