The San Diego Examiner makes an interesting case for why it is hard to sell art privately–without an intermediary–for most people:

The weakness of the market for privately sold art is measurable. EBay has made a large investment in its eBay Art program, but has not been able to achieve sales volume comparable to any of the established international art sales organizations. Here is an overview of common reasons that private sales of art reduce the value of the art:

1) Art sold privately without the support of an art sales organization often creates the appearance that no art sales organization will invest in advertising, sales training and inventory finance costs for the work of art. The main reason is usually pretty simple — and a good reason not to buy the art.

Seller’s Market for Art Poses Challenges and Opportunities (San Diego Examiner)