The point is that you can't just look for people who are famous or prolific on blogs or twitter or GitHub or whatever else.
When someone starting out in the industry asks for advice on how to get recruited, it's very trendy for wisened old souls on places like HN and Slashdot to mumble something about making sure you contribute to Open Source projects and have a GitHub account.
But on the big OSS projects, where making a contribution wins you significant geek cred, is anyone involved in a hire/no-hire decision really going to take a load of time to look through a bunch of commits you made and figure out whether they were any good and what sort of impression they give of you? IME, you're lucky if everyone making that decision even read your whole CV before the interview.
And on smaller projects, no-one recruiting you knows what they are unless they've shipped and have an obvious presence to see, in which case that is probably a far more effective advertisement than the underlying code anyway.
If you've got your own personal project, which is complete and something a potential recruiter can immediately run for themselves, then sure, include a link to it. Likewise if you've got a blog that's going to give an immediate positive impression and is clearly down to you personally, go ahead and include that. But those are things where you can immediately see the whole picture as a recruiter, with minimal time and effort.
I remain to be convinced that there is much value in linking to things like GitHub accounts or major OSS repositories, because they don't offer the same instant gratification. They do demonstrate that you're a keen programmer generally and not just in it for the money, but that's going to be all they do for most potential employers.
Other interviewers haven't mentioned the contributions at all. So I guess it depends on the interviewer.
But if you get to the point where you're discussing your contribution in an interview, you've already got past one of the big hurdles, and the guys interviewing you are now going to be forming opinions based on what you actually say to them personally. In that respect, contributing to an Open Source project or hosting something on GitHub didn't convey any particular advantage just because in theory the recruiters could look you up, and just giving a link to a GitHub account rather than highlighting specific contributions isn't really worth much at all.
My advice to someone wanting to stand out in those early days would simply be "Make stuff, preferably stuff that looks interesting". Whether you contribute to an OSS project or build something else makes little difference IME, and so I think the cookie-cutter "You simply must have a GitHub account and contribute to OSS" wisdom is just plain bad advice.
This is true, but not the point (at least until automatic tools run through the commit history and rate the contributions automatically).
Contributing to OSS projects gets you through filters, in the same way being Ex-Google will open a lot of doors.
The fact I'm an Apache committer and have code included in Spring gives me some credibility as a Java programmer (even if I haven't been active in either of those roles for years). Hiring managers are more likely to put you on the "worth looking at" pile rather than the "doesn't have a clue" pile based just on that.
I've gotten a cold-call email from a recruiter who started the email out with "I found your github account…" And all I have in there are two tiny personal apps I wrote to scratch an itch I had.