I said never, but thinking harder I actually bought some at school in the 6th grade (99 or so). They actually had a dispenser in the lunchroom; it was a blue box on the wall that you put in 75 cents and you got a floppy disk. Right next to it was a pencil dispenser. Never seen anything else like it.
I haven't used a floppy since 2004, when I got my first USB drive. It was 64 MB for $20, but even 64MB was ~30 times that of a floppy, and it was also faster.