Fair enough, that is indeed a – possibly major – difference, although Google department A sharing data with department B, which gives stuff to department C could be argued to be similar, as the size of these departments easily match those of other companies.
Google is different in this regard. Since they don't sell raw data, it's easier to opt-out (remove data via the Dashboard[1], delete your account, etc.).
[1] http://en.wikipedia.org/wiki/Google_Dashboard