Having spent my childhood immersed in the earliest RPGs; watched the appearance and evolution of home computers; and witnessed first hand the vast influence D&D had in shaping online RPGs; I find it rather poetic to watch the feedback loop complete its cycle, and see the online RPGs take their turn at re-shaping D&D. It does make for a very different game indeed, but different isn't always bad, and we learned a lot of valuable lessons about game design online. There's a few design choices in 4E I'd happily take issue with, but all in all, the things people gripe about the most were just as bad -- if not worse -- with older editions of the game when they first came out. Give it some time for the D&D community to soften the hard edges of the new version, and there won't be a heckuva lot left to recommend the older versions to anyone but their most rabid devotees. As far as I'm concerned, what MMORPG games bring to tabletop rules is far less problematic than what the MMORPG players themselves are bringing.
You can get problems in both directions, of course. Over the years, I've witnessed countless ill-conceived attempts by tabletop role-players to plug their expectations into an MMORPG setting, only to see all their best laid plans go up in flames because the social dynamic on an MMORPG is nothing like the one that goes on at the gaming table. For a tabletop game, you can take a proclomation like, "All dwarves would rather die than live in dishonor," and run with it as a universal truth in your campaign, because it's possible for five or six people to come to some sort of concensus on what dwarves would consider honorable. Pack a thousand different players of dwarves into one game, though -- half of them having only picked the race in an effort to max out their key combat stats -- and that one simple statement becomes a powderkeg as players abandon all sense of civility in the war to decide who gets to define dwarven honor. I know of such a feud on one MUD (aka: text-based MMORPG) that had been dragging on for about seven years last I checked, ruining the fun of countless players and admins alike.
Now it seems the shoe is on the other foot as more and more MMORPG players are getting lured into the ranks of the tabletop role-players by friends who play both ttypes of RPGs and by tabletop products marketed at the MMORPG demographic. Like all those tabletop gamers who came to the MMORPGs thinking they already knew the terrain, MMORPG players are showing up at the gaming table with their own potentially toxic preconceptions. Perhaps the worst of these is the drive to squeeze every last ounce of efficiency out of their characters' stats.
Power players have been with role-playing games for as long as the hobby has exsted, but MMORPGs take the allure of power-play to a whole new level. With direct GM intervention at a minimum, the experience is necessarily mechanics driven rather than story driven. Sure, it’s possible for MMORPG players to agree to conduct storylines among themselves, but the ability to make a real impact on the environment always starts — and almost always ends — with a player’s ability to game the system. To make matters worse, the repetitive grind of accumulating wealth/power by doing the same activities over and over (the faster the better) magnifies the effect of every tiny little advantage that players can eke out for themselves. e.g.: A +5% to-hit in a table-top game (where it should give no one pause if you swing your sword exactly ten times all evening) is nice, but that’s only a 50/50 chance it’ll change the outcome of even one die roll that night. In an MMORPG, on the other hand, where you might swing your sword twenty times in a minute, you could land 100 extra blows with that +5% before the tabletop players agree on where to order pizza.
Another concept that MMORPG players take to new heights is that of "game balance". That D&D 4E strives so hard to balance every class against every other class, every race against every other race, is one of its most MMORPG like aspects. In MMORPGs, it’s a huge deal for factions to argue back and forth, forth and back about game balance (which they invariably define as, “no one else can best us in combat — at least not with any frequency”). First one side cries foul; then the other side taunts it as a bunch of cry-babies; then the admins tweak the programming; then the side that had an advantage screams, “We’ve been nerfed! I don’t know why we even play this stupid game!”; then the balance of power shifts and another faction starts screaming bloody murder about the unfairness of life and of no-good, weasely game admins.
The thing that so many of these new players fail to understand is that as soon as you’re sitting down face-to-face with a game master, the whole nature of the activity changes. The GM can kill their 523rd-level, 65-strength warrior demigod as effortlessly as he can kill a 1st-level peasant farmer. There just aren’t any Joneses to keep up with anymore, so a player might as well ease up and enjoy the unfolding, highly personalized story and the company of his friends — because if all he wants is to prove his imaginary-martial-prowess, there are much, much better battlefields to prove it on these days.