It would appear that a gang of East European scammers are behind the CraigsList adverts and fake payment websites.
The scam has been investigated by the anti-scam community over the last few days. Fake site killing experts have been contacting hosts and registrars of the sites and drawing their attention to the fraudulent content that they are hosting on their servers. This effort has resulted in a number of the sites being closed down.
This action has angered the scammers, who have launched a campaign of DDoS attacks on prominent anti-scam websites. The fact that the scammers have resorted to this costly exercise is proof that the actions of the anti-scam community is effecting their illegal income.
Additionally, the administrator of one scam warning website received a threatening email, which threatened to 'eradicate' the website if the anti-scam sites continued discussing and acting on the fake payment sites.