It must vary by area. State Farm has no issue with a trampoline and 80% of the people in our area have one. We do not have one b/c my husband doesn't want to move it to cut the lawn, but I called to find out because my dd really wants one and I think as long as you have an enclosure and you don't allow multiple children on at a time it is OK. I know different strokes for different folks, though. Kids can break an arm or leg, but can on a bike. My neighbors child broke their arm on their bike, my friend growing up broke their collar bone falling off their bike. Accidents happen you just have to be cautious.
Just quick statistics on bicycle and trampoline injuries...just quickly googled just to give an idea on that in reality they are both just as dangerous for kids.
In 2001, 134 children ages 14 and under died in bicycle-related crashes.
In 2002, nearly 288,900 children ages 14 and under were treated in hospital emergency rooms for bicyclerelated
injuries. Nearly half (47 percent) of children ages 14 and under hospitalized for bicycle-related
injuries are diagnosed with a traumatic brain injury
trampoline injury rates were 70 injuries per 100,000 children ages 0- to 4-years-old and 160 injuries per 100,000 5- to 14-year-olds, for a total of 98,000 injuries that year