To me /. feels like it's been around forever. Partly that's because I was on it when I was a kid, but it felt old even then, I think possibly because its great rival (adequacy) had already died (since when K5 and Plastic are also basically dead).

I get a weird feeling when I think that it's less than twice the age of 4chan, which still feels new and exciting (possibly because I was there in its first year and have watched it grow).

Seriously. I was ~13 when I created my /. account, reading about Linux and running my first servers. Now I'm almost 30 and doing the same kind of stuff and loving it just as much.

That's one of the great things about this industry.

What other everyday profession is so interesting to pick up as a teenager and so amenable to learning professional-level skills without ever leaving your house?

Sure, you could start studying medicine or the law at an early age, but no one will let you practice those things without a degree. You can't get experience operating on a cadaver when you're 12 like you can putting together some arduino circuits or a Node.js web site.

I always found it amusing how much emphasis recruiters placed on where I went to school in my first couple of jobs after college when so little of what I felt I brought to the job I actually learned at the University level.