It seems to be a growing trend with the Valley startups but I have noticed some other companies on the East coast adopting the pattern. I can't really comment on the UK/Europe, I am based in Canada myself. Are there any sites that UK/European companies use instead of LinkedIn and Github? I'm genuinely curious.

It's getting more so. Last time I was looking for a job (UK) a recruiter not only mentioned my github, but asked me to pass on another job offer to someone he'd noticed I was collaborating with.

Oh wow, that's pretty interesting. Was the recruiter from a small company just trying to aggressively go after candidates or were they legitimately interested in you project? Not to undermine your work at all but it's the first time I have heard of an experience like this. Congrats!

Big recruitment agency. I think he'd heard the name of that specific guy rather than caring about what we'd actually been working on.