I'm fairly nerdy in a lot of ways (no surprise considering that I'm a physics major), but I've never been a computer geek. My brother is. He and I helped our dad build a computer when my brother was in fourth grade and I was in sixth, and my brother has been borderline obsessed ever since. As a result, he has to deal with being the guy everyone calls when he or she has a computer question.
He grumbles sometimes, but he's pretty good about helping people out. So when one of my mom's co-workers needed to buy a laptop for school, he helped her shop and find a good machine within her price range. When his friends' computers die, he works to diagnose and fix the problem. He recently built a computer for a friend.
These are generally not people who have lots of money to devote to tech support. If my brother charged market rates, most of them might no longer come to him. However, my brother has gotten lots of non-monetary payment in return for his services.
When my mother's co-worker bought a laptop, she used my brother's Best Buy Reward Zone account, and he got quite a few dollars worth of gift certificates. His friends often give him their old parts when they upgrade. The girl for whom he built a computer gave him her old one,which he gave to my parents, probably in the hopes that they'll let him keep his current computer, which they paid for, rather than make him give it back after he builds the new one he's planning.
On the whole, this underground economy seems to function pretty well. I did a bit of tutoring for someone whose family owns a restaurant and got paid in salads rather than cash, a win-win situation for everyone. Do you have any experiences bartering for your services? Do you believe you get compensated fairly, or do you feel pressured to accept less than what your time is worth?