Talk to other people on the water. You will know whether you are too close or not. If fishing with people you know, the rules are different. If rock fishing with your buddies, it's clusterphuck time.
If you plan on getting anywhere close to another kayaker, ask if they have lines down and if not ask if you can pass behind them.....most guys will let you know if its cool or not.
If in doubt, or someone is not very talkative, give extra room.
I do want to add, as soon as people start going bendo see if all these 200 yd rules stay in place. I can tell you from my experience that as soon as you get on even the most experienced, highly respected, sponsored yak fishermen out there have a way of sliding in really close.
Common sense is not so common anymore.