.... I've come to the conclusion that the best rule is to simply avoid all other boats if reasonably possible, regardless of size or type.... I also recommend that if a powerboater does alter his course for you, that you give them a wave to let them know that you actually appreciate that they've followed the rules. Doing so will help ensure that they continue to do so...
I totally agree with this. If other boaters see you as someone who keeps out of their way, they'll try to keep out of your way. If you're seen as "that annoying sailboat who's always in the way of our good time on our powerboat" then you'll just be asking for trouble.
Simply waving at other boaters as they provide courtesy, and sometimes just sailing the same general area of a busy lake (back and forth on the same line) can make you a much more respected boater. Just make sure that your line isn't in the way of an area that someone else was using.
Where I'm from, others generally see what's going on, and stay out of each other's way.