Worthless because, as in about every single sorry attemp to stop piracy, the workaround is consistent in a few modified jumps here and there (and so on) They are not more efficient than a CD-required protection and as easy to destroy.
As ever, annoying the custommer (broken key hardware, lost key, lost CD, ...) is what you get most. Pirates and worms do not care.
An online protection is far more efficient (still, there are workaround possible as long as the savegames are on the player's side)
