Sometimes, it's fun to jump on someone's wheel and coast for a bit, especially if they don't know I'm there. <flame suit on> If they do see me, I'll either back off or pass them for good. I would never do this on a road ride, but slotting in behind somebody on the ride home for a block or two isn't the worst thing in the world. If somebody does it to me, well, that's okay too, as I'm fine just ignoring them.