Craigslist, Flagging, Overpost, Spam - How much is too much?

The recent discussion on Flagging on Craigslist raises a few questions
in my mind. Clearly, you shouldn't flag someone if the only reason is
that you are a competitor. But, as far as overpost etc. goes, how
much is too much? Is it OK to post the same for sale 1x/ week? How
about 2x? Should you be able to post in 2 cities if you live half way
between them?

I, for one look at Craigslist a lot and really get sick of seeing the
same pinball wanted ads. Especially the Ohio ones "I need a pinball
for my kid, grandchild, I can't afford a Christmas and need a pinball"
Blah, Blah, Blah. Especially when it is in 3 cities. Also the guy
who posts the same 4 tired machines for sale 2x per week. It really
gets old.

Finally, how DOES the flagging work? Does one pull it off? or do you
need 4-5 flags before it goes? Anybody know?