People tend to find people they enjoy playing with, and stick with them. I know that when I have deliberately chosen new realms with some new characters, I have met with cold shoulders, beligerence, and even some outright OOC hostility. Needless to say, I will tend to avoid those people again in the future. That won't stop me from trying a new place or two, but I will probably try to find places they are not. So it will be more likely that I end up with the same subset od realm-mates again.