She was a head writer for SNL, she created the biggest comedy on TV, she wrote "Mean Girls" which is probably the most quoted teen comedy of the last decade, she's won numerous awards, and she's been starring in multiple films such as "Date Night" with Steve Carrell which opens in April. I don't think there's any questioning of her credentials.
The Vogue staff is pathetic. Their numbers keep going down and down and down and their covers look the same every month. Maybe it's time to try something new? I have a feeling that they noticed their sales were going down so the Vogue staff decided to take a risk and publish a cover that was quite different... That cover would be the Gwenyth Paltrow cover from 2008. That cover, although different, was horrendous - leading to even worse sales. After that, they probably thought that taking risks were just going to make things worse when in fact the only reasons things got worse and they didn't sell any copies was because that particular cover was embarrassingly bad. They need to know that they can actually try something new and make it work well. Just hire Steven Meisel again, or something.
They keep trying to appeal to the "average American," but they don't realize that they are in fact losing their main cliental which is people who actually like art and fashion. The "average American" is intimidated by Vogue and they're most likely going to buy Cosmopolitan no matter what - you're better off just catering to the people who want to read Vogue in the first place and don't like looking at such boring covers.
If Vogue published an issue with, for example, Vogue Italia's November 2009 exact cover with Rianne ten Haken - what's the worst that could happen? I can imagine people would at least wonder who that girl is and be intrigued to buy the issue. They need to experiment at least once.