I'd tend to agree since that (having kids) applies to me. There's clearly a filtering effect, probably eliminating more experienced people.

However, he apparently has no shortage of suitable talent available when using this method.

Not at all. You're saying "yes" to something instead of "no". You may go to a meetup, you may meet people through friends of friends, and you may place an ad on Craigslist. All of these things open doors to more people. The filtering was closing doors.

I thought the point was that people don't even apply because they didn't hear about the job. That's not filtering, that's just not casting an effective net in the first place.

When you have a surplus of people who can do the job, then you can afford to filter based on luck. In this case, limiting interviews to people like you who you will end up being social with, instead of people who can just do the work.

The problem, of course, is that the odds are good he's hiring people who are less skilled than some people he's filtered out. In a perfect market his product would get beaten by whoever hired those better candidates he ignored, but we live in an incredibly imperfect market and it probably won't make a difference.

Mostly you're adding candidates who like programming.

Yes, and if you get really good candidates (by going to meetups and being a nice person), then you can afford to do that.

I don't think he was saying exclusively hire from the meetups...he was saying to add that to your recruitment portfolio. There are a number of developers who aren't looking per se but by engaging them in a more social environment than a job board, you have a chance of catching their attention about the new job you're hiring for. The biggest thing that Raganwald never touched on is that many of the best developers won't even apply to your job under normal circumstances because they're content where they are. Getting involved in the community helps engage those people.