I think ethanol gets a bit of a bad press. We used to blend methanol into fuel in the 80s and that was really bad , and fuel line elastomers were changed to cope with the solvency power of this alcohol. Ethanol is much less aggressive than methanol, but it seems to get more brickbats thrown at it than methanol ever did.
Most premium fuel has 5% ethanol (10% in France) , but there are many other compounds used in blending fuels which can swell rubber. Obviously the blenders try to avoid the worst of them, but modern elastomers should be able to cope well enough. I suspect one of the problems is that OEMs tend to down spec rubber hoses in order to cut costs, and hence the problem has re-surfaced again.
