Here in Wisconsin, i believe it's first come first serve. I hunt out on the bay alot and there are probably 10 blinds put up. Now i hunt typically three days a week and sometimes don't see anyone using certain blinds for quite awhile.
Now i won't use another persons blind, but I don't have a problem setting up right beside the blind and hunting that spot. Only once have i had a problem with a guy, he was having a bad day, got there late and ran his boat through my decoys, we had a nice little chat. On the other hand last year i had a guy show up, didn't know a thing about where he was or how to hunt, but, he had a camp stove and offered to fix breakfast if he could stay and hunt with me.
This year i have a camp stove in the boat most morning, nothing beat a hot breakfast in the blind.
There is room for all of God's creatures, right next to the potatos and gravy.