- How many people, that are coders (*) are on Bitcointalk?
I went for this, although indeed the question is rather unclear; also it must be mentioned that there are many "levels" of being a coder and many coders didn't touch the code of Bitcoin or don't even know in-depth how it's working.
But, on the other hand, it can prove (or not!) whether bitcoin attracts mostly IT-related people. Imho that assumption is no longer true, for at least 4 years now.