Mike Davies works as a web developer for Yahoo Europe and has some insightful comments on the Internet Explorer rendering switch (see source).
When a user upgrades from IE7 to IE8, they will be upgrading from IE7 to IE7. When a user upgrades from IE8 to IE9, they will be upgrading from IE7 to IE7. Notice the trend. [...]
Effectively, with this meta tag proposal, Microsoft have either absolutely guaranteed that they will remain the dominant browser on the web, or it has sown the seeds for its ultimate destruction. If it's dominant IE7 will be the instrument to hold back all standards compliant progress, just like IE6 before it.
And the same happens in this case: if the browser vendor took its responsibility and improved its implementation, the whole issue wouldn't exist for webdevelopers' if their sites written to standards (and valid) don't display properly. So the whole "the users have to be protected from broken pages" card is a smoke screen in my opinion.
Just be frank then: corporate partners costcutting is more important to Microsoft than the freedom of the web.