Not at all - I'm saying not to make up rules at all. Watch the behavior, and if you think something is inappropriate, say so. Then if it continues, say so again, and take action.

The TOS should be something like:

    It's impossible to say clearly exactly what is and
    is not appropriate behavior.  Be nice, play nice,
    and don't be evil.  If I think you're behaving
    badly I'll tell you.  If you keep doing so you'll
    be barred.

    I intend to be fair and just.
    My decision is final.