It is clear that the media and its host of analysts are increasingly splitting in two camps on the Egyptian revolution: one that sees it as a wonderful expression of "people-power" that, left alone, will naturally culminate into some sort of pluralistic democracy, and another that sees only the Muslim Brotherhood, in other words, that sees only bad coming from the revolution. These extremist views need balancing. The fact is, depending on what the U.S. does—or doesn't—the result of this revolt could either be the best or worst thing to happen to the Middle East in the modern era.
For starters, that the Muslim Brotherhood poses a great threat, there is no doubt. If Mubarak goes and a power vacuum is created, the best positioned opposition group to take over is the Brotherhood—this is especially the case if there is no outside intervention to prevent it.
On the other hand, the majority of the hundreds of thousands of Egyptians protesting and dying in the streets of Egypt today are not doing so because they want sharia law enforced to the letter. Rather, this is a popular revolution in the literal sense, and contains all segments of Egypt's population, not just the Islamists. The only united goal all Egyptians have is to see Mubarak go—hence the ubiquitous Arabic sign, Irhal: "Get out!"
Therefore, rather than naively assume that this revolution will lead to a democratic Egypt (and so the U.S should stand by), or cynically assume that this is unquestionably an Islamist revolt that needs to be crushed (by supporting Mubarak and tyranny), the U.S. should simply do whatever needs doing to see that the revolt, in fact, leads to a secular and pluralistic society, which many Egyptians, believe it or not, would welcome.
The secularists are there. Now is the time to support them. Without Western support, the Muslim Brotherhood will take over Egypt by default. And if that happens, the Middle East will rock like never before in the modern era.