The likelihood of accidentally using E85 in a vehicle designed only to run on straight gasoline is pretty damn small, considering the difficulty of even intentionally encountering an E85 pump. Regardless, a group of automakers and petroleum industry officials are reminding consumers that fuels containing blends of ethanol over 10% (E10) are only for "flex-fuel" vehicles. Additionally, consumers are being warned that modifying standard vehicles to use higher blends of ethanol is not recommended. The corrosive effects of ethanol can cause damage to standard fuel system over time, and making the necessary changes to the engine management system calibration will almost certainly run afoul of the EPA and its myriad regulations concerning emissions compliance.
For those wondering if your vehicle is certified to run on E85, check the owner's manual, or go to the National Ethanol Vehicle Coalition's list of flex-fuel vehicles.