Craigslist is FULL of scammers. Beware.
Another scam that a lot of people get fooled by is the Overpayment Scam. If you are selling something on the internet or looking for a job (ebay, craigslist or private ad) the scammer will contact you and "buy" the goods, apartment, service or offer you a 'book-keeping' job and send you a cheque for more than the agreed price. They will ask you to cash the check and send the 'overpayment' back to them via Western Union.
The cheque they send will be a fake but the bank might not spot it for a long time so you will get the money initially but they will then come after you for a full refund and maybe even call in the cops too because you presented a fake cheque.