Now while I understand the risks involved with Trampolines I grew up with one in the back garden and it was THE BEST thing we had as children. All the kids on the street would come round and use it (they were a lot rarer then) so it was great socially. When it wasn't raining we were on it everyday and it really did keep us fit as kids. We even used to even sleep overnight on it in the summer! My older siblings have trampolines for their kids and they all love it and it will keep then entertained for hours. I think if you get one with a safety net and are strict about how many kids are on there at once (as most accidents happen with too many people on and them getting over excited) then I think it's a brillant way to get the kids out of the house. In New Zealand nearly every household has a trampoline and the majority of the population are fit and healthy. Now of course as fattothin pointed out there are risks, however there can be risks with a lot of healthy activities such as climbing, rugby, canoeing etc etc. I think if you make your rules for using it very clear and only allow older children to use it unattented then you will lower these risks.