I wonder how many employers actually search for (or would look at) GitHub repos? We are a bit biased here, right? Lots of folks working on bleeding edge projects leveraging lots of little open source projects--so, of course, we think "does candidate X have a GitHub profile?" But I reckon in many markets, many programmers might not even know GitHub exists.
Personally, I'd do some searching on a candidate, and would be rather happy to find code of theirs online, but I won't hold it against the candidate if the search doesn't find anything interesting.
My experience supports this. Most of the software we write is so far from the bleeding edge that you could safely lick it.
In all the years I've interviewed, I have only once interviewed someone with OSS experience (he was hired, BTW, but not specifically for that reason). I've seen resumes that listed OSS contributions that didn't make it past the phone screen though.
I've often wondered if it was just that many programmers don't think that their open source work is worth putting on a resume since it wasn't done in the context of a day job.
That's my feeling too, that this stuff is hot for the startup / dotcom hiring people which is a minority of the programming jobs out there, which are mainly intranet business stuff.
Personally, I'd do some searching on a candidate, and would be rather happy to find code of theirs online, but I won't hold it against the candidate if the search doesn't find anything interesting.