Ethanol-laced gas (10 percent ethanol today, 15 percent soon) isnt all bad.
Just mostly bad.
It reduces fuel economy noticeably (because theres less energy in a gallon of 90 percent gas plus 10 percent ethanol than there is in a gallon of 100 percent gas).
It makes food especially meat more expensive (because not-far-from-half the corn crop is currently diverted to ethanol production, not livestock feed).
It enriches politically powerful agribusiness cartels not the American farmer (not that the American farmer has any more right than an agribusiness cartel to force others to buy his product).
It can also cause problems in older (and especially occasional use) vehicles and power equipment not originally designed to withstand high alcohol-content fuels.
The main worries are: the alcohol eating away at rubber and plastic parts not made to deal with alcohol-rich fuels and corrosion (from water accumulation courtesy of the alcohol in the fuel) eating away at the insides of metal parts such as metal gas tanks and fuel lines. Both of these worries are more likely to become actualities if the vehicle car, bike, lawn mower is left unused for extended periods of time, in particular because of the increased likelihood of moisture accumulation within the fuel system and also because E10 (thats what gas is nowadays) doesnt have as long a shelf-life as 100 percent gas. It goes bad sooner leaving you with problems.
Regular use is the first thing you can do to avoid the ethanol blues. Run whatever it is for at least half an hour at least once a month. This will keep fresh fuel (or at least, fresher fuel) in the carburetor which will mean less moisture in the carburetor. If its an old bike, turn the fuel tap to off just before you shut down the engine and let it run until the carbs are empty. Do the same with lawnmowers and so on that also have on-off fuel taps (and if yours doesnt have an on-off fuel tap, consider installing one). This helps avoid problems associated with gummed-up carburetors caused by the fuel sitting in the bowls dissolving rubber seals and so on and corrosion caused by water in the fuel.
Also try to top off the tank when youre done. A full tank is less prone to moisture forming inside from condensation/heat cycling and the new fuel will help freshen up the old fuel thats still in the tank.