i disagree with the monetary restrictions and would never enter a world with such restrictions, even though im already in a world that has a 100 mil player payroll cap (kenny powers). but that's just my personal opinion and i understand everyone likes to play this game their own way (hence the 100+ worlds out there). i do think almost everyone would agree that a minimum win requirement for major league teams is a good starting point for private world rules. the only world i commish is the bigs which was recently ranked the #4 private world in hbd (for what that's worth) and the only rule we have (which was just adopted one season ago) is a minimum wins rule of 50 per major league team. the number of wins can vary from world to world but i would think 50 is the minimum of any world that would bother to have a rule in place at all.
i think the bulk of a responsibility of a private world to remain a quality private world, however, is on the commissioner.
i also think a good blog goes a long way towards keeping and attracting owners to a private world. its not easy to maintain, and ours has slacked a little bit over the past two seasons, but something is better than nothing. i honestly think that if your world has a great blog that is updated semi-regularly (like the bigs' is) that the world will be more attractive to serious, long-term owners which i think every private world desires. a great bog is almost, if not just as, important as league rules. everyone loves to read about themselves and the blogs are super nerdy, lets be honest. but so is HBD to begin with, so why not go all the way, eh?