...Ever noticed that since Alonso's 2 world championships it's always looked unlikely for the reigning World Champion to defend his title? Each year the reigning World Champion seems to drop back to midfield. Red Bull are the only team to have stayed at the front for more than one year in a row since I've been watching.
So you think there's been some manner of sea change in F1 since MSC won WDC five consecutive seasons?
You're making far too much of what were an unrelated series of coincidences. First, that is too brief a historical period to take any significant conclusions from it. Second, look at the circumstances.
After 2006, Alonso changed teams, a move fair guaranteed to scuttle a driver's chances for a successful defense of the WDC.
Räikkönen won the 2007 WDC and then retired. Choosing not to compete has proved to be 100% fatal to one's chances for defending the WDC.
LH won WDC in 2008 but could not repeat owing to the freak season of 2009.
The FIA changed tyre specs too close to the start of the 2009 season for Bridgestone to fully respond so the rear tyres were too narrow to achieve balance against the fronts. The very definition of serendipity, Brawn were the only team truly able to cope with the FIA's cock-up by virtue of the Toyota-developed shadow diffuser. Their advantage (in the dry) was so unassailable, it was a certainty that the WDC would fall to Brawn. Yes, Vettel came second in WDC but only because Brawn came 1-2 three times in the early season, with Barrichello always coming second. If Button had faltered, Barrichello, not Vettel, would have claimed WDC.
And for 2010, the WDC has once again changed teams.
Since JB is mathematically eliminated from repeating as WDC, in the four seasons since Alonso last won WDC, the World Champion has changed teams twice, retired once and, in the fourth instance, was selected by the double diffuser lottery. I see no pattern at all.
What I do see is that RBR scored 29 WCC points in 2008, 143 points out of the chase. In 2007, they scored 24 WCC points, 180 points behind first. This hardly qualifies as "staying at the front."