First, Islam isn't homogeneous. The Sunni sect, which is probably closest to what most people think of as "mainstream Islam", considers the Shi'a to be an aberration, and "not good Muslims", because they follow a lineage that isn't recognized as "official" by anyone but themselves. Then there are the Salafis (one version of which is Wahabbi, OBL's native religion), which are again different. You could look at these "sects" kind of like the "demoninations" in Christianity - the Catholics believe in the Pope, the Protestants don't, and each claims the other is "wrong" in that regard.

The difference is, that most Christians don't fight over that stuff today. But many Muslims do. That's the root of the sectarian violence in Iraq, for instance. Politics and religion are deeply intertwined in Islam, and so if someone's religion is "wrong", then their politics must be "wrong" too. In a way, this situation is reminiscent of the divisions in Ireland, where the politics around the religious divisions have (recently and historically) resulted in armed conflict.

Then, there's also the idea of a "secular Islamic state", which realizes itself in various forms across the globe. Many "traditional" Muslims aren't happy with that, they consider that concept to be an oxymoron. The smart ones choose to work within their respective political systems, but the more extreme mindsets are willing to actually their beliefs into overt violence.

I don't know about you, but I don't see this situation changing anytime soon. The last time pan-Arabism and pan-Islamism were significant geo-political forces, was during Nasser's tenure. One of the interesting pieces here, is that the Internet has become a pretty central player in this equation, globally speaking. Suddenly like-minded peoples who were previously isolated, are able to communicate and coordinate with nothing more than a personal computer. And there are many examples of Islamic encryptions which our intelligence agencies have so far deemed to be "unbreakable".

It seems to me, that we (the United States) must tread very carefully over this turf. It will be very easy to overplay our hand, or over-react to situations that bother us. The Muslim sensibilities are very different from our own. It seems to me, that it would be wise to be aware of that.