RSN48 is correct. The later arriving boats must not interfere with the previously anchored boats. They need to adapt or go elsewhere, or ask the earlier boat to make some sort of change that would be conducive to everyone (that last would rarely happen).
There are not only some boaters who don't know or care about this really common sense "rule", but this year there seems to be a large number of "new' boaters.
Earlier this summer, we arrived in Prideaux Haven (main part) to find a fair amount of room. I decided to try out an anchor buoy for the first time, and put out about 3.5-1 scope for the high tide mark also taking into account the height above the water to the anchor platform while free swinging like the vast majority of previous boats. No trouble for 2 full days. Then this one guy comes in and proceeds to drop his anchor within a few feet of my marked anchor, and then backs over the buoy. I yelled at him (not angry only to be heard over his idling engines) about my buoy being under his swim grid and that he might not want to tangle his props. He told me not to worry as he was going to stern tie. He was anchored well over 150 yards from the shore. Then he sent one male crew member ashore with a "non-floating dark coloured line' in a soft floored inflatable dinghy rowing the line ashore. He got to within about 100 feet of shore when he ran out of line. The skipper then yelled to him to row harder to "pull the 35 foot" main boat over to shore. The whole process took over 1.5 hours, and they ended up adding in a second line (added length) and being tied about 90 yards from shore at an angle.
Another boater who was stern tied a bit further down, went over and informed them that what they had done was dangerous to other boaters, especially kayakers, dinghies, etc. All was quiet at this point, and I heard the "offending" boater blame my anchor float for all of his problems??? This, even though there were at least 10 empty shore tie chains on the other side of the bay, and 2 more empty ones a bit further down from where he had chosen to try out this "keystone cop" episode (he had one problem after another).
Eventually, he let out more rode and pulled in more stern line and ended up where he should have been near the shore with his bow facing out.
Luckily for me, he did not snag either my anchor nor the chain rode and he did not foul my buoy line either.
Anchorages can get crowded with people anchoring closer than is normally comfortable. As long as everyone communicates, tries to be nice, and the later boats realize that they are the ones who must accomodate if needed, all usually goes fairly well. I will say, besides that fellow above, I did witness some interesting ways to anchor this summer