Reminds me of the "most stupid thing" I ever typed into Terminal.app. I somehow managed to create a subdirectory named "~", and decided it was a good idea to do this:
rm -rf ~
If you want to try a fun little experiment, type this command into your colleague's shell and see what happens (and how long it takes):
> mkdir ./~
$ time mkdir ./~
So, when i delete a directory, whenever possible, i use the rmdir command. rmdir refuses to delete a directory which isn't empty. It's a really handy safety check. If a colleague dropped a tilde directory on me, the process would go:
Well, i'll just delete that.
$ rmdir ~
rmdir: /home/twic: Directory not empty
$ rmdir '~'