Never helping anyone with technical stuff unless you're getting paid (or whatever similar thing you can think of) is over-correcting for the doormats that can't say no
I stopped helping people, in general, when there were several instances of people telling me that whatever I did the last time I touched their computer caused some random problem 6 month later. That, and it seemed that people were getting upset when I would show them how to do things, within a couple of minutes (from just knowing where to navigate), that they had been struggling with for hours, or that they were, in fact, typing their password wrong. Maybe they weren't upset with me, but it was usually a negative experience for me, and it slowly chipped away at the glee I used to have for helping people.