I think that art that happens by accident is some of the best kind. It comes off as a suprise when you arn't sure what the end result will be. Take paint darts for example. The best part of the project is the excitement you get when the dart hits the balloon and paint explodes everywhere.
Another example could be when artists smash things into tiny pieces, or throw things and make them shatter. Destructive art could be used in many ways, but is it purposeful? What would critics say about art like this?