Leave it to Malcolm Gladwell, author of The Tipping Point, among other great books, to see parallels between PitBulls and prescription drugs. Here's the link, and here's a snip:
This is a paradox that is not confined to dogs. For instance, for years people in the pharmaceutical business have been aware of the fact that a large number of reported adverse reactions to a particular drug can mean one of two things. The obvious meaning is that a drug is dangerous. The other meaning is that a drug is SO much better and safer and more effective than any other drug in its class that it tends to be given to the sickest and most troubled patients.
Exactly why we have to be very careful when looking at data and statistics. There usually is a lot more going on than you might think.