You usually see it a lot when people get those mIRC debug worms that spread, and you instruct someone to remove them. Some of the "better quality" worms will write thier own unload alias, so when you type /unload -rs worm.mrc it'll just spoof an unload message but do nothing. in this case, you'de use /!unload -rs worm.mrc and it unloads successfully.
