Thanks to Yvonne Jacques for sharing this New York Times article. Apparently, serious collectors are buying big bucks art from digital images only. But they usually know the reputations of the artist (often have seen other works by the artist in person) and the dealer.
This is a good time to remind you how important it is to know how to handle digital images. Learn about pixels per square inch (ppi for digital images–as opposed to dpi, which is for printed matter–thanks for your insight, Robin), how to resize your images, file sizes (as opposed to image pixel sizes), and how to attach them to an email. If you're dealing with large images (over 10 MB), there may be a time you have to learn to FTP them to a site. You can cross that bridge when you come to it. In the meantime, realize that anything over 1 MB will send people with dial-up into a tizzy. You have to learn to resize and to ask for desired file sizes from the requester.