Repeat offenders or serious first time offenders are removed and not allowed to return. They have NO unnecessary rules. Enforcing three rules that are clearly stated is easier than tracking every tiny violation of some pointless commandment. The first is rigidly enforced. Abuse is simply not accepted, even if the target of the abuse says they don't mind.
Abuse is anything that the listowner feels is abusive.
Even if they're not posting regularly, the listowner always knows what is going on. The listowners generally make a point of encouraging beneficial relationships among members. This not only helps the members, but creates a more durable feeling of having a stake in the community than just the usual banter. If people get REAL assistance that positively impacts their offline life, the community aspect quits being the usual fragile thing that lists have, and takes on a very significant role. If people have something at stake that goes beyond the list, they are more likely to protect it.