I realize this is a question with no single right answer, but I find myself curious today as to other people's perspectives. I'm just a few hours removed from a trip to a local fishery where people frequently don't give a very wide berth, but where one nimrod in particular really got under my skin today. I was working a run downstream, swinging a couple soft hackles, and rounded a bend to see a guy working his way upstream. Neither one of us was beating a path, but after a while, we closed within pretty close proximity to one another. We both continued fishing for awhile without getting any closer, and when I felt I had finished with the water in front of me, I reeled in and walked around the guy to continue downstream, making some small talk as I passed about how the fishing had been going, and then re-entering a respectful distance downstream of him. I took a second to change one of my flies, and as I was finishing up I heard footsteps behind me. It was the guy I'd just passed, now walking in downstream of me, close enough to where the end of a long drift from me and the beginning of one from him might have tangled. I couldn't believe it. In one move, he'd cut me off from any further movement downstream, unless I wanted to get out again and go around him. Keep in mind he'd seen me working downstream before, and he had been working up previously, so there was no reason for him to come back down, other than the possible fact that I was a few steps away from one of the better pools on the stream, the one he'd just started casting to.
Anyway, I get home tonight, having mostly forgotten about this joker, and happened to see a thread on another forum where a guy was complaining about a couple of fishermen that were working their way downstream toward him on a stream, out west maybe, and he described trying to tell them diplomatically that he thought what they were doing wasn't cool. When one of the other fishermen asked this guy what he expected, he supposedly told them they should give him or any other fisher 500 yards. My reaction to THAT was: 500 yards? Where in the world do they give that much space? It struck me that here's a guy getting offended when someone comes within 500 yards of him, when my personal hopes are probably more like, I don't know, 50 yards or less?
So hence the question, what's considered crowding in your mind?