I remember tracking down corrupt entries in our DB. It was mostly one user introducing the inconsistencies. Turns out he would double-click on every button, and

I remember tracking down corrupt entries in our DB. It was mostly one user introducing the inconsistencies. Turns out he would double-click on every button, and the browser would happily send-abort-send two requests every time. Sometimes these would race on the server. We implemented disable-on-submit after that, and the inconsistencies went away. Other people would click again when the response didn't come fast enough, but that was rare to lead to corruption. Probably when their connection was lagging, they would click multiple times in frustration. But that one guy provoked enough destruction to make us notice and fix it for everybody!