Regarding Jenson, Vettel squeezed him at the start (legetimately of course) which forced him to dropped down to 8th (or 9th if you count webber as well). Jenson had to lift off to avoid Vettel's car, or he would have lost his front wing. I think Jenson is now thinking about the big picture, the championship. One DNF with a win from his main rival would cut down his lead massively. I think he feels like he can't take any risk.
Moreover, I don't think we should mark him off just yet because of this one race. The car hasn't been great in the past few races. But he was just unlucky in Valencia. If you look at his laptimes at the end of the race when he was chasing Alonso, he was consistantly pumping in solid laptimes, with like five 1:39.0 in a row (and another 1:38.8) which was pretty impressive.