I'm sorry, I have to call bull about 3e's marketing not talking about what didn't work in 2e, and how they were going to change things for the better in 3e. Take out your old dragon magazines and look at the race and class previews.
Heck, they talked about what didn't work in 3.0 and how 3.5 was going to make it better, when they were doing the marketing and roll out for that revision.
The 4e designers just did what the 3e designers and marketers did when marketing the new edition. They said that they found this mechanic or game philosophy problematic so they are removing/changing it because it works better. You may disagree with that decision, but it wasn't like they went around saying "3e sucks and only stupid people play it."
Now if I was to point out the biggest mistake of 4e's marketing, it would probably be the cancellation of dragon. It would have been fine if dungeon and dragon were ready to launch and provide content when they canceled the magazines. I think Dungeon could have been canceled without too much trouble, because it was never particularly popular or profitable. There would have been howls of protest of course, but Dungeon wasn't needed for marketing the new edition and fewer people would have mourned its passing. Dragon on the other hand would have been a good source of marketing in the hobby shops, which is not an advertising medium one should give up on easily. Once the new edition was out, that would have been the right time to move Dragon to an electronic format. I'm absolutely sure that it was the right decision in the end, and that DDI makes more money for wizards than Dungeon or Dragon ever did, without the headaches of distribution and printing.
They compounded their error of shrinking market coverage by making all their previews only available to those that provided their email address to view content. That meant that casual surfers of the website were left out, while only the hardcore online community was let in. If the hardcore gamer didn't like what he saw, I guarantee that the rest of the established gaming group of more casual players isn't going try 4e based on what the hardcore gamer tells them. What is more, the hardcore are usually going to assume the worst and are the most resistant to change.
If the previews had been available to all, then you have a direct line of communication to 4-5 guys, not just one.