Tim Vasquez has posted up a detailed meteorological analysis of the weather conditions associated with the loss of Air France 447 over the Atlantic (h/t SO). He concludes:

Overall it does appear weather was a factor. In the main MCS [mesoscale convective system] alone, the A330 would have been flying through significant turbulence and thunderstorm activity for about 75 miles (125 km), lasting about 12 minutes of flight time. Of course anything so far is speculation until more evidence comes in, and for all we know the cause of the downing could have been anything from turbulence to coincidental problems like a cargo fire.

The complete lack of a radio call, though, and the clear evidence that the plane’s route crossed through an active complex of thunderstorms does make it likely in my view that structural failure from turbulence occurred.