My last dog destroyed my brand new wallet within 20 mins, it was my bad for not wondering why she was on my bed and being quiet for 20 mins. One thing i can say without a doubt is my last dog would have never caused physical harm to a person (unless they were paralyzed, then she could possibly have licked their skin off their face) yeah she required exercise but it's better walking around with a dog that absolutely loves people than walking around the block at 2 am by yourself.
As for your argument, nah I don't deal in predators normally. That being said, having a pet Shark is on my list of "things to do when I get rich"