micropython/micropython — pull request #929 by dhylands (2014-10-25 00:45:41+00:00)
Title: Added mention about using USB charger when resetting the file system.

It seems the Mac will happily wipe out at least some of the data on
a freshly reset filesytem, if the filesystem was reset while plugged
into the Mac.

See: http://forum.micropython.org/viewtopic.php?f=6&t=358