Rooms in Exchange for Sex

So apparently there's this website that offers people the chance to post listings for... well... anything. Some of that anything is for apartments in exchange for sexual favours... terribly bizzaro! Apparently it's not against the law because posting the ads is not illegal only if someone were to go into such an agreement does it cross the line into illegal.

The host of the website trys to keep such things off the site, but as it's a free forum it's hard to blacklist all such listings. He relys on subscribers to the page to inform him of inappropriate listings and some slip through the cracks....

So here's the site:
http://www.craigslist.org