I check craigslist every now and then and try to find some snakes. Mostly they're just normals, and some people who are small time breeders put ads up.
I found an adult female het pied for $350 on there a month ago. He said she was proven. I emailed him a few times, and the last e-mail I sent was asking about her health, and if I could see any of the pieds that she produced. I didn't get any emails back after that. Wasn't a big surprise, who would sell a "Proven het pied female" for $350?!
Just like everyone else said, if you are interested in getting a snake off CL, be sure to ask as many questions as you can think of.