Here is a cautionary tale about a roommate scam. http://www.yiyu.us/im-stuck-in-the-middle-of-a-roommate-scam-please-help/
The description of the situation and the advice in the comments is worth reading. Note that the person will be okay because he was alert and thought the setup was fishy. When dealing with people on Craigslist it is worth being aware. NEVER exchange money without having already gone through the entire selection process and checking references.
As noted elsewhere on this blog, Craigslist has a page on scams. The first rule is only deal with someone you meet in person! Read the rest of the rules. There is also a list of organizations to contact if someone tries a scam on you.