This is a segment of sheist's link....

"Loosely defined, entrapment is a situation in which, if not for the actions of the police officer or police informant, the defendant would not have committed the crime. This defense is generally only successful in situations where law enforcement officers create a criminal plan, plant the idea of that plan into an otherwise innocent person's mind, and then instigate the plan for the purpose of prosecuting the suspect. "

So, if the post on craigs list is explicity asking for pot, sure sounds like entrapment. However, I wouldn't do it. Even if it's not a cop, it could be a crackhead ready to stab you and take your stash... or worse...