One interesting nugget: more than half of the 200+ employees at Stack Exchange are working on StackOverflow Careers. Has anyone used SO Careers? Opinions?
In contrast, GitHub was surprisingly disappointing. Maybe one or two worthwhile candidates, and a ton of junk. It appears that GitHub's jobs get scraped and posted elsewhere, and the bulk of responses to my ad were low-quality (and that's being generous) candidates responding to those reposted versions.