\But if your letting your cat out into the world, you really need to ask yourself where it is going, what it is doing when it is out there.
In many places, it's already an issue. I don't have a definitive list, but there are hundreds of species that are now extinct or endangered specifically because of cats. One species is actually extinct supposedly because of the predations of a single cat. Fragile or naturally isolated ecosystems (ie, islands) are at high risk.And since we oppose destroying them, huge colonies thrive with human aid where they might otherwise thin out. I wonder it this may become an issue.