I've been tempted to before, but it's just stupid. Why would you risk failing a sac, or unit because of it, and if you do the work beforehand then you'll get a better mark than anyone who cheats anyway.
As for personal anaecotes, this one guy at my school (tech-head) managed to hack into our school's intranet and subsequently into whatever place the maths methods sacs were kept, printed out a couple of coppies and shared them with some of his friends... everyone who he shared them with failed that sac and he failed the unit (only year 11 so though it didn't matter that much). The stupid thing is that he has not got bellow 90% on a freakin' maths test in his life- he would've aced it anyway.