If Google penalises then would it not be easy for competitors to take actions against you to lose your site rakings? If that happens then the index will turn into a bun fight and Google will no longer be able to function.
Clearly there are cases where someone is caught red handed (JC Penny) but for a lot of the other situations, for example dodgy links that could have been bought by the site owner or one of their competitors, isn't it more likely that they would just be given a nil value?
