13 teams x 3 cars = too many cars.
But 8 teams (the 2009 teams minus BMW and Toro Rosso) x 3 cars = not too many.
I think maybe it would have been a good option to do this, rather than admitting all the new teams. Importantly, you'd make a tight championship race much more likely. But since the new teams have been admitted there's not much they can do now.