The problem is that the age-factor is too clearly against the older guys. If drivers are more or less on a similar level (which I think Rosberg and Barrichello might be), younger drivers, who have more years left in them and more room for further improving, are preferred. Also drivers like Trulli and Heidfeld could be left without drive for next year, while much younger guys like Glock, Sutil and even Kovalainen are more likely to find a drive. If Barrichello was 10 years younger, nobody would try to get him out of that Brawn seat. Actually, those same 10 years ago in 1999, when Rubens was also very impressive, he was linked to both Ferrari and McLaren drives in the silly season rumours, one of which he finally got.