Given the desperate need for new revenues (along with drastic spending cuts), Nate Silver explores the idea. Money quote:
At least based on this back-of-the-envelope sketch, creating one or more tax brackets at $1 million and up, and levying taxes upon them at a 3-5 percent marginal rate, could fairly easily offset a 1 percent or perhaps 1.5 percent tax increase on the middle class. That doesn't mean that we wouldn't eventually need to consider middle-class tax increases as well, although my preference would be to achieve them by means of a carbon tax, which would fall fairly heavily on the middle class if it weren't offset, rather than an increase in marginal tax rates. But it can certainly be a part of the solution and it seems irresponsible not to discuss it along with other ideas.
I don't like raising taxes on anyone, and I sure don't like the stigmatization of the successful. But we've got to find the money somewhere - and that's where most of it is.