The Hadoop Offline Image Viewer tool has an undocumented 'feature' where it will silently delete the directory passed in with the -t flag. This blew away some important files when someone used a sensible, but ultimately poor choice for this directory as the deletion isn't documented.
For example, if someone were, as root do: 'hdfs oiv -i fsimage_00000000000307052343 -p Delimited -t / -o image', bad things would happen. This behavior should be documented and probably have a dialog or throwing exception.
There is a piece of code from PBImageTextWriter where a check can be added: