The scam is certainly not anything new. ArtQuest reported on the scam as early as 2004:
Thursday, October 14, 2004
Ripping off Artists Online ArtQuest, an online gallery for artists is warning its members of an increase in scammers trying to rip artists off. Over the past few weeks they have had more than 15 members contact them in regards to scammers. Problems with cashiers checks (cheques), credit cards, and international money orders have been reported.
ArtQuest has started a list of art scammers, along with some information about avoiding these kind of people.
I personally get at least two emails per month from a Nigerian, first letting me know what paintings they like, then asking how they can pay immediately. Their name is different each time, so I hope no legitimate Nigerian art collector ever contacts me by email because they get deleted immediately.