According to an article in the Oregonian, 2/10/08, ethanol can harm small engines. This is because it attracts water, the water and ethanol separate with the ethanol sinking to the bottom. The ethanol then corrodes parts it comes in contact with. The bits can then get into the fuel line causing additional problems.
Oregon law has mandated gasoline to be 10% ethanol.
To avoid this, using fuel stabilizer (we carry Opti-Mizer) in every tank of gas will keep the gas from separating.
Also, keeping the gas tank relatively full will help prevent moisture from accumulating in the tank by giving it less room.
The story in the Oregonian focused on boats and other small engines such as lawn mowers, but the information is applicable to scooters as well.