As for "Filtering resumes by having an account at a single specific site. . . is rather arbitrary": I never in my post say that's the only mechanism we use to

As for "Filtering resumes by having an account at a single specific site. . . is rather arbitrary": I never in my post say that's the only mechanism we use to qualify - we get candidates from all over the usual candidates (monster / cb / hotjobs / dice / etc) but we use SO to help qualify. I see lots of value in SO when trying to filter through the HUGE amount of resumes that come through the door. I hire lots of technical people, this system works for me. Their business model is charging $500/month to hiring managers for access to candidates and slapping in some advertising. The fact that they’re out on the road raising VC says that they’re probably having a lot of success in this model because it works for others too. StackOverflow centralizes, VERY VERY SUCCESSFULLY, a huge talent pool of programmers. And it gives hiring managers a lot of data that is hard to collect (multiplied x30 resumes a day) from a variety of “programming forums” to make hiring decisions.