That said, there are, of course, a number of problems inherent in online tabletop gaming that like to accompany all of its wonderful advantages and stab you in the back when you look away. Imagine trying to play a sit-down tabletop RPG with every player in possession of a laptop, iPod, phone, or other electronic accessory. All the time. There is a reason that I greatly dislike it when players bring such items to face-to-face games, and try to discourage them from doing so. The distractability factor for players is simply too high. During whatever element of gameplay a player does not find interesting, he or she is likely to tune out - but this is very problematic later, when details from that period of time become important.
"NO! We were allied with those (hob)goblins!"*
(A completely out-of-context Order of the Stick panel! Used for an unrelated joke!)
Access to electronics is an unavoidable part of gaming online, and though it isn't insurmountable, it certainly causes problems. It also has a kind of sickening synergy with the reduced rate of conversation in online games - few people can type as quickly as they can speak - and so there may be (perfectly reasonable) pauses in an online game. Added lulls combined with easy access distractions can mean trouble, even in a situation where the DM hasn't made any mistakes.
We're about to have a campaign run with both text and voice-chat, though. I'm very curious to see how that will go. The distraction factor is still present, but this might be mitigated by the slighlty faster clip of gameplay (ideally).
*He knows. He just doesn't care.