Scott, As one who sells their work regularly via many venues and has done so for some time, I can tell you this is not entirely true anymore. The world is a far bigger place than any one gallery can cover. I am selling prints via the Web to places my galleries haven't begun to try to market my work. Plain and simple, the way you and many think of galleries and gallery representation is rapidly changing. Some are getting with the program, others are already being left in the dust. The book is still being written on this subject and it looks better for the individual artist than is does for galleries I am afraid.
Bill - I'm not saying that the market is not changing. I'm just stating that this is a risk of selling your work on ebay. I think it would also depend on the pricing you set, and if you are selling via Buy It Now or are auctioning your work, if it is limited edition or if it is open editioned. It will be very interesting to revisit this issue in 10 years and see if the art market has caught up, or if it has changed for everyone.