In case you have any confusion about the quality of fuel produced by large amounts of agricultural welfare payments, check out this video on what ethanol does to aluminum and rubber parts:
This is pretty enlightening, too:
And, finally, a motorcycle guy tosses in his several cents:
With all of that said, I have been only marginally careful with my "end of season" fuel. I have used Stabil since the late 80's, anytime my bike is likely to be unridden for more than a few weeks. In my carb days, I often disassembled those damn pieces of plumbing for various reasons, mostly altitude changes. The inside of every one of my bike's carbs were spotless. Seriously, they shined like they'd been polished. The same goes for my snowblowers and lawnmowers. They are the only carbureted motors I own now and I do an inspection at the end of every season. I do try to keep non-ethanol, non-oxygenated fuel in those motors or run them out with Stabil in the last tank before I store them.