They don't cause running problems, just storage problems. Then again, any gas that is stored over time will cause problems, no matter how pure it is. The Gasoline will evaporate, and leave behind the additives, and then those evaporate and leave behind the varnish. So depending on the additives in the canned Gas product, it may or may not evaporate faster than pump gas, so storage in a plane is unknown.
Pure gas will boil at 100* F, additives keep it's boiling point higher, so it stays liquid at higher temps, so it will store longer. Ethanol boils at 173* F, so it is less likely to evaporate, so the longer gas is stored, the higher the concentration of Ethanol to gas occurs, and that is where the breakdown of the components can occur. Some components can't survive in pure Ethanol, but can take small concentrations of it without ill effects.
The fuel line that was in my John Deere weed wacker turned to mush and basically disintegrated when I had stored it with a half tank of mixed fuel. The lines were clear tubing, so no idea what they were made of, but the gas was an ethanol blend, and the device was purchased after ethanol was already in our gas, so it SHOULD have come with fuel lines that can handle it, but apparently did not. The carb though had no ill effects, just the lines.
I'll bet with the proper fuel components and tuning these little motors would run just fine on E85. They wouldn't fly as long, or have as much power as they do on 91 Octane, but they would still work OK.
The problems I have with Ethanol in the gas has nothing to do with the fact it is in there, but more in the fact that ethanol is heavily subsidized and the use of it has raised food prices up to artificial levels. If the subsides were removed, it would be too expensive to farm, harvest and produce it here, and would be more economical to have it shipped from south america where they produce it from sugar cane far cheaper than we ever could. The problem with that is, the government has put a ban on imports from that country. The green movements that initiated all these programs has so far had FAIL boat written all over them that it really is hurting the overall progress of truly finding an viable alternate energy source. It would be great to have a truly cheap form of energy to fly our planes with, especially with the cost of glow fuels being so high, but so far, ethanol is not it, at least not with the current method used to produce it,