Cats are like people; all different. Some are contented to live in a group as long as there are resosurces (food, attention, space) for all, and others want it all and don't want to share. Cats are born with a base temperment, and then their nurturing and life experiences build on that. In any case, there will be a limit for how many cats that a particular situation will comfortably support. The way to find out what that limit is will be to go over the limit. The limit will also varry depending on the personalities that make up the group. I have four cats, and there is one who has made it clear that she no longer wants to be a part of it.
There is another interesting aspect to cats and territory. Noted animal behaviorist Patricia McConnel gave a prgraam on cats that I went to, and she pointed out that in the wild, preditory animals will have a territory and defend it from all comers. Cats, however, have a time-share. Cats, especially outdoor toms, will have territories that overlap. They will partol their turf, avoiding others as much as possible. One will usually come by in the morning, another might usually show up in the afternoon. Wonder why your cat stops in the doorway deciding if he's going out or not while you stand there holding the door wishing he would make up his mind? He's reading the area to see who'd been here recently and who might still be around, so he doesn't walk into a confrontation he doesn't want.
