This time in the middle east. First Tunisia, now Egypt. These were both "moderate" states that had the support of the US. Mostly, these so-called moderate states have been repressive to some degree in the governance of their populations. In Egypt, Mubarak has been in office since Anwar Sadat took a bullet. Mubarak has remained in office via bogus elections and other shenanigans. He has consolidated the power of the state around himself and like any dictator, is loathe to give up his power and priviledge.
Who's next in the cavalcade of toppled despots? Saudi Arabia, maybe? The US supports these so-called moderate states for a couple of reasons. One, US foreign policy favors a benign status quo. So long as despotic leaders can keep their countries in some mode of continuing stability, the US is willing to overlook repressive governance in that pursuit. Two, these states get their nominal label of moderate in that they are not wild-eyed eager to wipe Israel off the map. They may not like Israel, but they have come to some accommodation with its existence.
The US finds some alternative form of government in these moderate middle eastern countries about as welcome as poison. In all likelihood, the new regimes will be hostile to US interests, to some extent. Envision the change in Iranian government in 1979.
Tunisia and Egypt aren't important players in the world energy situation. However, change of government in Saudi Arabia could be a very unsettling experience.
The current Saudi regime won't go down easily. All those many expensive arms that the Saudis have bought from the US over the years were acquired for purposes beyond the repulsion of external threats. The Saudi royal family and the extended oligarchy that runs the country had in mind internal threats to their regime as well as attacks from outside.
As I see it, the US is in a no-win situation in the middle east. There's no way the divergent interests can ever be reconciled. The US would like to have easy access to oil, peace for Israel, and recognition for individual human rights. It ain't gonna happen.
As to recent events in Yemen, that's not much of a story. Yemen has been in turmoil for decades. I can recall doing a current event report in junior high school on the civil war in Yemen in the 1960's.