[motomotive1]

All US tanks are prone to warping and bubbling, possibly due to ethanol in our gasoline. Ducati is working on a new tank, rumors that these are now being shipped. No reported problem on bikes outside US.

This may be a separate issue, but my dealer seems to think the reason this happens on U.S. bikes specifically is because of the EVAP canister. If I understand correctly, what happens is that if you fill the tank all the way to the absolute top what can happen is a pressure buildup (probably due to heat on the tank itself) and fuel can flood into the EVAP canister essentially plugging it up. At that point there is no place for the fumes/pressure to go and the tank warps.

Some of the newer Ducati's have a sticker on the tank that warns not to "overfill" it. It says to fill it only to the bottom of the filler neck and no higher.

I haven't read through the complete tank thread so this might have already been covered/debated but it makes sense.