Am I the only one that really doesn't like Quora's answer summary? Especially for a question like this, because some (somewhat contrary) valuable opinions are essentially ignored in favor of a catchy one liner.
And I agree with the earlier posters - age is a big factor here, and not just because of the additional self-discipline and knowledge that it tends to produce. Assuming that you're starting something in a field you already know well, you probably have a lot of people you can call on for advice, help, resources, etc., not to mention more than a few credits in the favor bank. In other words, you're really not as solo as you were in your early 20's. Nor are you as likely to spend as much time trying to define your market, identify your customers, and work out your acquisition costs.
In other words, your need to iterate is probably a lot lower, since and older founder is more likely to be operating with a measure of specialized or otherwise hard-to-get insight, and are aiming for something specific that isn't low-hanging fruit, and that may depend - critically - on well established relationships.
From what I understand, the tech world is one of the few places where founders are commonly so young. I've lost the citation, but I believe the average age for start-up founders in the broader economy is 38.
Same here, basically. I'm not opposed to joining up with a co-founder or two (in fact, I'm actively seeking them) but I'm not going to stop working just because it's only me at-the-moment. F%!# that.
Posting here on HN; tweeting; emailing old friends, former co-workers and asking them; standing up at meetings like TriJUG, TriLUG, etc. and announcing that I'm looking for a co-founder; hitting up the recruiters who call trying to recruit me; asking other local entrepreneurs; running a "Hackers & Founders" meetup, etc., etc.
And I do have a couple of irons in the fire, including one acquaintance I've known for a while, who is in graduate school and is interested in possibly joining me once he graduates in a month or so. Also one former co-worker who may be interested. It's been a slow process, but I'm not eager to jump in bed (so to speak) with just anybody either. I'm looking for somebody who's passionate about startup-life, willing to go "balls-out" to succeed, and - ideally - has a complementary skill-set to my own.
After several years of learning the tools, I have more to offer, and I'm much more prepared to evaluate a potential co-founder. But that's only because I HAVE been doing it alone.