While I am definitely in the anti-pitbull camp, I think what is really sad in all of this is that there are going to be some lovely dogs out there that get destroyed. They are going to be someone's pet and its going to be extremely hard for everyone. Whether they should be in the home or not, how do you explain to children that their beloved family pet has to be put to sleep? What is going to cause enormous problems is that there is no way to clearly identify which dogs are the "right" cross breeds, and some dogs who don't have a drop of pit bull blood in them could be wrongly destroyed.
As has been previously said, this problem is bigger than just pitbulls. There should be much tougher restrictions on all dog breeding, compulsory de-sexing of non-breeding dogs, compulsory training sessions etc. It will probably mean dogs and puppies will be more expensive to buy, but IMHO if you can't afford the initial purchase price then you really can't afford a dog.