if fishing a tight spot id think 10m is a fair distance? to be honest im not realy bothered if someone pulls right up next to me, i guess it all depends on who it is? and there abilitys? as long as they dont tangle my lines, and pull in if a decent fish is hooked its all gud in the hood.
swell,current, and conditions like wind should be a factor. fishing areas like clifton where geting as close as you can to the reef, you should expect people to crab next to you, its just what people do.