Why errata is more complicated in D&D
I love and hate errata. I like to have rules work better in my game, so I like when problem areas in the rules are amended. I hate when errata becomes so extensive as to make books irrelevant. Here are reasons why we should push for as little errata as possible, I think:
1. People want to use their books, and continuous errata makes those books less and less valuable. Of course, if you play the game with computer tools, then things that make computer games better, like patches, help improve it. But as long as this is a game that people and WotC want played at a table with friends, the books matter. The books are where the company makes money, no? Of course, this could be made better by a good set of online and distributed electronic tools for playing the game, but I already think this should come with the game anyway.
2. Despite the strength of Dannager's example of Magic the Gathering, that model doesn't work well with D&D. For Magic, the game is competitive, match-style, and turn-based. The 'tournament' style game that Magic is lends itself to more acceptable errata. D&D is different - people are looking for rules to facilitate a fun game experience and to resolve disputes and conflicts neutrally. So the "lots of minor updates" style of errata is good for Magic, because it is a different kind of game and regularly changes editions so that the rules stay current. It is bad for D&D because people are not really looking for that kind of investment in the rules themselves all the time - I don't want to have to check every two weeks before my game to see what has changed so that I can teach my players the new rules changes.
3. As much as I wish we were beyond sloppy work with multiple fixes, we're not. 4E is the worst offender, not necessarily because it had the most problems, but because it made the most effort to fix them in a timely manner, and that highlighted the kinds of problems regular errata can create. It was terrible overall. To take advantage of the game as it is now, people need to be using the character builder, and taking a long time to investigate the various options. 4E messed up basic stuff, like the math for skill challenges, and when rogues could get extra damage. Fixing it didn't make things seem better - in fact, it was much worse, because people knew they had been sold sub-par rules in the beginning set. I know no one is perfect, but I want the people I pay for a product to be pressed hard to do the best they can, and not have whole rule subsets destroyed by some basic mathematical analysis within the first two weeks. Saying, vehemently, "I want a game that doesn't need fixing" is better than leaving the other options open.
The game is evolving, though, and the more people are able to use good electronic tools, the more liberty designers will have to "fix" after production. But even then - seriously - take the time to get it right.