I don't understand why a Mercedes winning the championship will sell them more cars. Mercs aren't exactly your 'everyman' kind of car, and I guess *most* of the F1 fans are your 'everyman' kind of person, ie not buying £40000 cars every year.
What I'm saying is, if Merc won the championship, I wouldn't feel any more or less inclined to buy one of their cars. Same with Ferrari etc. Because I'm pretty sure very little from the F1 car translates into their current road models. The brand awareness for these guys is huge anyway, they could pull out of F1 today and people would still know who they were. Yes, I know it might affect future cars with KERS and that stuff, but that doesn't particularly bother me either.