It's easy to make a mistake, and as Ernie Gann wrote, "In this business, we play for keeps."
My daughter is a private pilot, and I recently finished her tailwheel endorsement. Since she needed to build a little time in the Citabria for insurance (she's all insured and flying it herself now), we did a little cross country. After buying fuel at the self-serve in Tillamook, we were in a rush to get the airplane out of the way for an EMS helicopter who also needed fuel. All good, until we got home and realized we left a fuel cap in Tillamook, and streamed A LOT of fuel out the open filler. It could have been much worse.
The good news, as I'm sure we all know, is that Turbo Commanders have an anti-siphon valve! Not so on the Citabria.