Warren Ellis has an excellent piece on the differences in the webcomic and digital comic medium:
All of which is Bleeding Obvious, of course. “Digital Comics†– paygated digital files in a wrapper for delivery to a device or walled up in a browser – were the business model that everyone interested in “comics on the internet†was looking for.
There is some excellent stuff in the piece, which would be done an injustice if I just quoted parts of it here, so mosey on over there and have a look what you think!