[pyre]

It will overwrite the hidden partition. The 'outside' partition doesn't know about the hidden one. When you are mounting the outside partition you do have an option to protect the hidden one by providing the password for the hidden one, but if you don't, you can end up overwriting it by filling up the outer partition.

[colanderman]

A-ha, I think this is what I was missing. Thank you.

That said -- I would think that a random blob of data sitting around on the hard drive is still highly suspect. Aren't hard drives zeroed from the factory? And wouldn't any true "garbage" data be decidedly not random? (Even if it's compressed... you would still expect to find headers etc. somewhere.)