Lessons? Don't start alone. Pick your co-founders really well (think "marriage"). Make sure you have people you really want to work with who are ready to leave their jobs and work for less money because they really want to work with you.

I think the lesson here is that if loneliness is a big problem for you, you might not want to start your own company.

But ideally you've got some smart friends that aren't completely risk averse before you decide to start a company, and those are probably a good set of folks to bounce it off of. I'm always dubious of people "finding" co-founders through systematic searches. I'd known my co-founder for 3 years before we started our company, and it's amazing how much more you learn when the pressure is turned up. I can only imagine that a lot of startups fly apart at the hinges when there isn't some basic level of getting along that's preexisting.

My old friend, and first employee, is too risk averse to join a startup in a normal environment. But since the company he was working for went bankrupt and he wasn't able to find a job for months, he gladly came to work for me and it has worked out very well.

My point is: intensity introversion introversion inherently limits the the size of any useful social circle by requiring excessive emotional energy to grow beyond that. For me, that size is probably on the order of a couple dozen people, though that's well beyond the comfortable level of emotional expenditure, which is closer to only one dozen.

Filtering by technical aptitude (notwithstanding a disproportionately high ratio) and startup compatibility, reduces the number to zero.

What about introverted co-founders?

Well, that depends strongly on the person, doesn't it? :)

Apologies for sounding trollish, but I'm somewhat shocked at the reactions here. We have someone telling us that they work themselves into such a lonely place that the only thing keeping them sane is HN, and yet no one is suggesting he reorder his life and find a better balance so that he can find more enjoyment.

I don't think you're sounding trollish, but I do think you may not be treating this forum as a casual social setting in which people sometimes make statements to convey a feeling, rather than because they are literally true.

Edit: I forgot to say:

I also think that for a lot of people who hang out here, and to a lesser extent on proggit, etc, this online community really is one of the most fun, engaging things they have available to do. Conversation online with those who are interested in similar topics could easily trump conversation in person with those whose interests bore you. Even if we grant that being in the real world is an important attribute of "fun things to do", it's unlikely to be the most important.

Reason is, it is about locking yourself up, getting through alot of the problems on your own and working on the next one. The minute you have someone there (even if they are coding as well) and when your task is not integrating it becomes more of a distraction having someone there.

For me, youtube, hacker news and sydney morning herald get me through my lonliness when im hacking away, also the odd trip to subway to get myself a sandwich and the lady at the counter :)

Then again, that has its own challenges. I've tried to work with several different uni friends in last few months and it's astonishing how many things they have calling their attention leaving little to no time for the start-up.

What I do is lock myself deep inside a little library cubicle. Then when I need some fresh air, I chill out by the student union. Talk to buds. And return to work. It really helps that my product is hyper-focused for the college market.