Yesterday I wrapped up my 2010 Home Media Overhaul and Documentation Festival with a blog post on why to watch TV. But I left another unanswered question on the table: why document your TV setup?

Documentation is somewhere between a neurosis and a calling for me. As much as I love a good geek-out, a weekend (or week, or month) spent sorting out some new tech system or software workflow just doesn’t feel complete until I’ve documented it. After all, if I haven’t documented my new system, how useful is it?

Think of this as the contemporary equivalent of the old question “if a tree falls in the forest, and nobody is there to hear it, does it make a sound?” If that tree were an undocumented software installation or a hardware upgrade, the answer would be no. OK, maybe it would make a bit of a thud (or a beep, or a ping) but if you came back the next day or week, you’d find that the tree had completely disappeared. All the surrounding trees would be moaning and wailing, “we want to fall over, too!” and you’d be useless to help. Or maybe you’d come back to the forest on a really cold day, desperate for fuel, but unable to remember how the f**k you’d gotten the tree to fall over the last time.

Documentation is the solution to all these problems. And thanks to the electronic-y goodness of the Internet, can be accomplished without hurting any trees at all: in fact, much of the best documentation can be found not in a book or magazine but in a blog post, forum or web page.

That’s because documentation embodies the very best of web culture. It’s the part of the web that focuses not on what we need ourselves, but on how we can help others. Go to Amazon or e-Bay, or for that matter any porn site, and it’s all about what the web can do for you right now. Go to a blog post or forum and you’ll find people using the web to help others.

I’m regularly astonished by the generosity that people extend through the documentation they post online. And by documentation, I don’t just mean the “here’s how to make that error message go away,” or “here’s how to build your own Linux box”. I’m talking about every single “here’s how I did it” post on the entire Internet. From the shoppers who share their experience with international shipping costs to the DIYers trading plumbing tips, the Internet is full of people going the extra mile to ensure that their experience can benefit someone else.

Certainly, there can be an element of selfishness at work. My blog post on how to use Thesis to customize your teasers started with me jotting down a few notes that would help me remember why I’d added some code to my blog’s setup. My post on how to make a great iPad app was intended as the raw material for a Harvard Business Review post. My write-up on how to get into graduate school gives me a quick answer (“read this post”) to all the people who e-mail me for advice. How to use your iPad for family multitasking is a cheat sheet for my kids’ future psychotherapists, and should save me thousands in their billable hours.

But each of these documentation efforts went far beyond its original, selfish use case. Somewhere along the line, the need to jot down some notes for future reference turned into the project of making my hard work useful to other people.

What motivates that effort — and makes it rewarding — is the transparent impact on other people. When someone tweets to recommend something I’ve written, or leaves a comment thanking me for mapping out a workflow, or e-mails to ask follow-up questions, I know that my documentation effort paid off — even if it just helped a single person. But when I think about all the workflows or tech fixes that took me dozens of hours to work out, saving someone else all those hours feels like a net gain for the human race. The urge to document is the urge to find one of those collective opportunities to extract a little efficiency.

Anyone who has ever blogged the steps in their latest craft project, tweeted their latest café discovery or written a practical response to a LinkedIn question has yielded to this documentation urge. It’s the urge to take what you know, and share it with others. It’s the need to maximize the impact of your time and effort by ensuring it has as wide a reach as possible. It’s the generous impulse to take the solution you’ve just found, and make it useful for anyone who needs it.

In that generosity lie the seeds of a new way of relating to our fellow human beings. Once you’ve subscribed to the belief that if it’s worth doing, it’s worth documenting, you can’t constrain your kindness to the Internet. Pausing in the doorway to hold the door for the man a few feet behind you; scheduling lunch with a new colleague so you can share your experience and tricks for doing business at your company; taking that old bike and cleaning it up so it can be used by another family: all of these modest, generous actions stem from the same underlying recognition that if 5% more effort can solve a problem for someone else, it’s worth doing.

If our lives online can help us commit to that 5%, the impact of our blog posts and forum comments and tweets will go far beyond the people who read them, beyond the value of the problems they solve. Our documentation projects will be our reminder of what we can achieve when we go beyond simply meeting our own needs, and amplify the value we create by thinking about how that same effort can benefit others. We’ll stop falling silently in the forest, and notice all the trees standing around us, wondering if they can fly.