Had a VM that batch processed files but some reason a couple of the files comming in was causing the procedure to crash and Gigs of files to get clogged.
I was moving big chunks of those into the host tmp Dir (only place I knew was ok to throw rand stuff) to try and catch the offending files. TMP was actually a RAM disk, so I filled all availability memory and crash the HOST system (including multiple other critical VMs) and lost weeks of data (because you know I put it in a RAM disk ...).