Did you happen to catch all the commotion on Hacker News? Blanket statements like "when it comes to hiring, I'll take a Github commit log over a resume any day" tend to fire people up (probably why the poster chose that wording anyway). Don't get sucked in.
If a company is lucky enough to get so many responses to their job posts that they have the luxury to throw away applications that don't point to some sort of OSS contribution, then power to them. But not everyone can be Google or 37signals. Even they know better than to make such absolute statements. There are always alternatives as DHH points out.
Is a readily available GitHub account more convenient? Of course! Hiring good people takes time and dedication, so anything that eases the vetting process is always welcome. There is also a cultural component to this. Some companies are heavily invested in OSS and only want to hire folks that are of the same mindset and culture. And that's perfectly OK. But it seems people are reacting to this hiring approach as if it were taking over as a one-size fits all; it isn't no matter how much it's hyped up to be. Just because a household name shop does it this way does not mean that every company will. A smart company will first take a close look at the type of candidate this approach would get them and whether they would fit their organization. Just think of this scenario: a shop prohibits any type of corporate code sharing and does not allocate business hours to their coders to contribute back to OSS. Yet somehow, they manage to snag a major GitHub committer. Do you think that new hire would last long in that work environment? No, so why spend time and resources hiring in this way? Same goes for job seekers. If you are not the OSS committer type or can't do it at work but you understandably value your personal/family time more than night-coding, then a shop that heavily favors GitHub committers might not be the right fit for you anyway. There is still a myriad of non-OSS shops out there that are dying for your non-public mad coding skills.
The point is that there are many ways to prove that one has what it takes to do the job. Amongst programmers, code is king, so providing samples is a great way to showcase one's tallent. Is a GitHub commit log the only way? Certainly not. One of my favorite companies when it comes to hiring approaches is ITA Software. They've actually gone to great lengths to setup a process where anyone has a chance to prove they have what it takes. Google suggests people practice on TopCoder before interviewing with them.
So don't get sucked into the hype. Case in point: if you are a big-data storage (nosql, hbase) or full-text search (lucene/solr) expert, you happen to have worked for say Google, Facebook, Rackspace or some other big-data shop but you've had no time to commit to a GitHub project, have no worries! We will definitely take a look at you at Traackr. Prior work experience will always count, especially if you have been already vetted by top-notch employers in the past. We still value resumes and we will find ways to look at your code.