I recall it was also not unheard of to have floppy drives that could be incompatible with each other. A drive that was a tad slow might format a disk that would work for itself, and other drive, but that disk might not work in a drive that was a tad too fast (and vice-versa). This wasn't common, just frequently enough to occur so occasionally as to always be baffling, particularly in an office with lots of PCs.

Then there were things like Spiradisc (https://en.wikipedia.org/wiki/Spiradisc), which created incompatibilities by design.