It isn't Craig's List that is to blame, it is thieves and scammers....
I understand the gist of what you're saying, and I'm not trying to start an argument, but I feel that CL definitely shares the blame. They thrive on providing anonymity to anyone and everyone, regardless of whether they are breaking the law or not. These scammers and thieves use CL because they know that they can remain anonymous and CL will do nothing to help the victim unless a warrant is provided by authorities - even if you can prove that you're being scammed!
How many years did CL allow prostitutes to advertise on their site before the law intervened shut it down? You can say that CL didn't provide the hookers, but they provided the venue for them to advertise for business and CL merely looked the other way. This is like saying it's not the motel's fault that prostitutes use their rooms, but if the motels didn't rent the rooms by the hour they wouldn't appeal to so many prostitutes, or their johns.
CL is negligent, and that doesn't excuse them in my book. Believe me, I can tell you from first hand experience that they will do nothing to assist a victim, even when they are given proof that a crime has been committed - and the California Penal Code substiantiating the claim.