Maybe feature: Refuse to write to mounted filesystem without a --force?

[icefoxen]

This is really on the edge between "assumes way too much about what the user wants", but also really heckin' nobody wants to do a block write to a mounted filesystem by accident. I know I sure as heck bite my nails and check four times when I'm doing something that could risk it.

That said, having that feature may simply encourage complacency, when you accidentally write to an unmounted-but-important filesystem instead of the device you intended to write to. Hmmm.