I interviewed at three companies over the course of a few weeks once, not one asked me about anything on my GitHub profile nor about my blog (200+ technical articles). I was a bit miffed. At the last one I asked to see the CV they’d been given; the recruiter had removed those links from my CV. (This was in Austria.) So had I worked on open-source or blogged solely to get a job, it would have been a complete waste of time.