I spend a good bit of time in the winters placing structure for crappie on the lake I fish. I have close to 100 spots fixed, so if I head to a spot and someone is on it, I just go to the next. If they are lucky enough to find it, then I don't blame them for fishing it. I do try to minimize it by placing structure in the winter when noone else is out there. I also put it out in spots where people wouldn't normally fish (usually in the middle of the lake somewhere with no other structure). The way I look at it, I have so many spots fixed that I or anyone else who happens to find them can't possibly fish them enough to put any kind of pressure on them.