> 1) Once someone starts paying you, they get to exert their influence on your work, and it becomes a lot less "hobbyish."

Definitely. I've been working on a free open-source project for 6 months. Last week, a user came with a feature request, and stated that they were willing to pay me. That could sound nice, but I immediately thought "nope". I told them that donations were appreciated, but I wasn't going to do commissioned work.

I don't want that kind of responsibility for my hobby projects.