While I've dealt with the occasional deadbeat buyer and even deadbeat seller, the idea behind craigslist is genius and I've certainly had many more positive interactions than negative ones. I would also say as a former HR employee for small business craigslist provides an essential service for low cost recruitment.
Child Safety should be red as there is (a) Adult content (b) links to sites that are scams, spam and contain malicious content (c) ads posted by scammers and spammers.
Not all of the site is bad, and it is the unethical users that seek to cause harm to others, therefore, child safety should be rated red just as a warning to other WOT users.
It's an internet classic and will probably stay this way. It's consequently filled with poorly administrated content and filled with adult content aswell. Use with caution, however i've heard of many people who love it because of the possibilities it provides.