Many accidents with inflatables are due to improper staking or tieing off.
All slides are top heavy and it is vital that they be tied securely so that they don't lean or tip over in the event of a power loss. The U.S. Consumer Product Safety Commission just released a safety bulletin on inflatables and it stresses how to tie off the inflatables.
All stakes should be 36"-48" long and driven 75% into the ground using the appropriate angle for the soil, weights if used should be 75lbs per tie point for small inflatables and 500lbs per tie point for slides. Also the C.P.S.C. recommends 2 attendants for all slides over 15" tall.
For accident reports, search http://members.aol.com/rides911/accidents.htm
or read the U.S. Consumer Product Safety Commissions' report
on Amusement Ride Injuries. These sites contain scary information but if you search for "inflatable" you will see that there are relatively few injuries reported from inflatable rides. What this site can teach you is how to avoid accidents by reading the cause of the reported accidents. This is a MUST if you are purchasing a slide over 12' tall.
Other Safety Information
Directory of State Amusement Ride Safety Officials