I can report there is a difference of opinion among engine mechanics over the harmful effects of alcohol. The last time I took my weedeater in for service, it needed a new carb. The reason was the check valves for the primer bulb had swollen and hardened. The labor cost to repair would have been more than the parts cost to replace so I got a new carb. The mechanic told me he almost never saw those kinds of problems before ethanol, but now it keeps him in business. My own personal experience agrees- my dad had a chainsaw he used every fall to cut firewood. It probably went 15 years without a tuneup or any kind of service. Now my weedeater needs a carb kit about every 3 years, as do many of our plane engines.
I do realize there are alcohol resistant rubber parts for 2 stroke carbs now, but I still am not convinced that they stop all of the problems that ethanol causes.