D&D and all RPGs are still most enjoyable when played around the table with friends. I know that's not possible for everyone, but no technology will ever change that basic fact.
I haven't tried play-by-Wave yet, but was involved in a number of play-by-e-mail games back in the day. I'd say PBeM can be just as fun as face-to-face, it's just a slightly different kind of fun. It's less of a social event, and there's less instant gratification. But a well-done PBeM can be very rich in a way that's hard to do face-to-face. You don't get that instant rush of gaming (very often, anyway) but you do get much more time to think about what you are doing and saying, which can be really helpful for the "role" part of role-playing.
Not true, its where cameras and shit come in. I honestly can't solve the logistics problems of playing DnD with friends in different states weekly :P
I'm starting a new long-distance campaign this week actually. I was disappointed to find that Skype doesn't support multi-way video chat, as my friends and I are in three separate locations.