"Aggressiveness" is in the eye of the beholder though -- Aussies should also be deemed "aggressive" for their nipping in that sense. I think that BCs are on the list along with ACDs because they have a strong drive to work and eventhough they may not be aggressive in the sense that they are going to maul someone, they probably have and do injure people on a regular basis because of their strong herding drive. I can't begin to tell you how many times I've come home from school and HJ says "Charlie really got so-and-so's ankle again today...". Yes, he has bruised and even drawn blood before, but it is never anything major, and to him it's a "game", a "job", he isn't doing it TO injure the person.

However bottom line, an injury is an injury, no matter the extent, and I think that's the basis they are going off of.