Going waay back to the original question, my only concern about digital comics is the same I have with e-books. They should be a compliment not a replacement. If too many lazy people see them as being a replacement (both in terms of having to pay for them - just like e-books I'm sure you can find "free" copies if you know where to look) that could cause problems for those of us who actually enjoy having the physical item - both from an esthetic and from a collector's point of view.
Unlike e-books, however, I don't immediately fear digital comics spelling doom for print comics or comic shops. But I am concerned that it might render print versions as "instant collectables". And by that I mean if Marvel, say, decides it will only print 1000 copies of Captain America because it does most of its sales in digital, you're going to see the same biting and scratching for those 1000 copies as you see when a limited-edition action figure or premium edition of a comic becomes available. And those who want to read the print version are going to have to pay through the nose. (I remember back in 1989 Mad Magazine came out with an edition spoofing the Tim Burton Batman movie. Even though the Mad was still available at the local corner store for $2.99 or whatever the cover price was, several comic shops started putting $10 on their copies, just because it had Batman on it. And guess what - they sold because people thought they were collectables. I wouldn't put it past some shop to start slabbing and jacking up the price on "rare" print editions of the latest issue of Wonder Woman ...)