Comment 3 for bug 476013

I'm pretty sure it's a bug: if you insert an unformatted disk and ask Nautilus to format it, it'll fail. If you insert a formatted disk with some non-standard format --- my USB floppy drive supports a format with 1kB sectors, for example --- Nautilus will claim to succeed but the disk won't actually be mountable. Some formats will actually seem to work, but the disks won't be readable if you try to use them in a non-Linux based computer.