In Mac OS X Mountain Lion at least, if you Option+click ( Alt+click ) on another a window of another app, this will make the other application to gain focus, and the current app to be hidden as if you'd pressed Command+H.
Is there any way to disable this behaviour? Perhaps with some
defaults write like command entered in a terminal?
I'd like to use Option+click for some different behaviour (moving windows by Option+clicking anywhere on them, using a third-party tool, Zoom2), and having Option+click trigger the hiding behaviour instead is very inconvenient.