Artists are the target of various scams, some resembling Nigerian Money Laundering scams, others tailored specifically to artists.
Scammers seem to know there's an abundance of artists out there who are trying to be seen in a sea of images, so some scammers focus on the promise of exposure, traffic, and sales. At best, you may waste some money, at worst you could be cleaned out. Be especially wary of buyers who offer to pay more than your asking price if you refund the difference. This not only sounds screwy, it is, and you could end up giving away your work and quite a bit of your money, too.
A lot of "scams" aren't really scams at all in the "legal" sense; they are just bad deals. Some sound like a good idea, and if done right, they probably would be...but they are frequently not done right.
Some time ago I started a Journal on my Red Bubble site, about Scams. It has evolved, like my Copyrights Journal, to include quite a bit of information, much of it contributed by other RB members, so be sure to read the comments, too.
Click the link to read the Journal:
ART SCAM INFO
My own opinions on the ones that are not illegal, just bad deals?
Vanity galleries, where you pay to rent space...the gallery gets paid up front and has no motivation to promote or sell the work. Often lacks vetting of artwork so your work may be amongst crap. Serious buyers rarely go there because they know this.
Another one is people asking for art for free, in exchange for "exposure." Read Janis Zroback's Red Bubble Journal on that topic:
EXPOSURE, A SLIPPERY SLOPE
Enjoy the reading, I hope it helps you avoid being taken to the cleaners!