I'm not the type to anchor off someone else's campsite, but as far as traveling or trolling go, I try to avoid campsites that are occupied, but usually the folks want to talk. I don't mind if someone goes by my site while they are traveling or trolling, if they catch a fish there good for them (I haven't seen this happen yet however). When I see folks go by that are close I'll say hi and ask how they're trip is going et. If its really windy there isn't much you can do but hug the shoreline and inevitably you go by a campsite or two.

With all that said, with the time of year that I go (sept or late august) I don't usually see a whole bunch of people and usually they are while traveling or portaging.