b. If craigslist establishes limits on the frequency with which you may access the Service, or terminates your access to or use of the Service, you agree to pay craigslist one hundred dollars ($100) for each message posted in excess of such limits or for each day on which you access craigslist in excess of such limits, whichever is higher. Craigslist TOU
Needs a little bit of context but from what I can tell it is basically saying don't spam the site. If you do they will try to claim damages in the amount of $100 for every post you make beyond the allotted amount.