Your dog, if he could type, could post an ad: "One cat, slightly used, free to a good home," and that would be fine by Craigslist.
The only protection you've got is common sense. Craigslist does provide a decent list of security basics. These include such fundamentals as:
1. Deal locally with public you can meet. To, which I will add, meeting them at midnight at the back of an abandoned warehouse, unless you're Jack Bauer.
2. Never use wire services, like Western Union. I didn't think it was that bad, but Craigslist says that anyone who asks you to use one is a scammer.
3. Be very, very wary of postal money orders and cashier checks. Many of these are fake, and if you get stuck with one, your bank is not likely to be understanding about it.
4. Never, ever give out your financial information, and yes, that includes PayPal.
In short, being paranoid in real life may be a mental illness, but when it comes to buying things on Craigslist, it's smart.