Doctors and chiropractors love trampolines. They keep the waiting rooms full of kids that smacked into each other, fell to the ground or got whiplash. Smaller kids, especially, are very susceptable to neck related strains and other injuries on those things.
I would never have one on my property. Ever.
Teach your kids and set rules, and have an enclosure and that stuff really isn't an issue.
Heck, ER's love jetskiers...I know I've given them plenty of business in Hawaii, Daytona, Louisville, and I think somewhere else just can't remember.