Craigslist killer- is Craigslist liable? Can hookers be charged?

Can Craigslist be held liable for the Craigslist killer using the service to meet up with prostitutes and rob/kill them? Also, I hear that he chose hookers on Craigslist because he thought they wouldn't report the crime. Do police usually charge crime victims if the victim was committing another crime like prostitution? What if a prostitute robs a john? Should he come forward? - Is this your question? Add additional information