Vogue had planned to put Miley Cyrus on their cover, but following her disastrous MTV performance, the fashion magazine changed their mind.

Apparently, Anna Wintour found Miley's performance inappropriate:
“Anna found the whole thing distasteful,” it quoted one source as saying. “She decided, based on Miley’s performance, to take the cover in a different direction.”
When asked about the magazine's decision, Vogue's parent company, Conde Naste declined to comment.