That's their prerogative--they're trying to sell a product.
I personally think IE6/7 users would be better served by ditching IE entirely--preferably to a WebKit-based browser. Others might suggest Firefox. Others would say to grab the latest IE. There's even some weird kids who might suggest moving to Opera ;-)
We should not implicitly advertising any browsers.
Not to get off topic, but to throw it out there, we can avoid the problem of not recommending any particular browser in a method similar to Microsoft. [1]
Of course, that begins to get into more work than is reasonably needed for this. While I'll be the first to say that people really ought to not use IE7 at this point, I agree that asking them not to isn't really our decision, especially considering the mission statement of the Wikimedia Foundation, as mentioned earlier.
If it turns out there is something significant that we can't do because we must support IE7, then I'll be all about dropping support for it in order to move forward. But without a very good reason, I don't think that is the best way to go; at the very least we should wait for their usage to go down. 5% of ">2500 per second" [2] is still quite a number of readers.
Thank you, Derric Atzrott
[1] http://www.browserchoice.eu/BrowserChoice/browserchoice_en.htm [2] https://meta.wikimedia.org/wiki/Wikimedia_in_figures_-_Wikipedia