I actually have used a LART before, but not one as satisfying as described. To elaborate:
Background: in my day job I'm a sysadmin for a medium sized non-profit composed mostly of social work majors. One of these days I'll explain the implications of this.
Everyone that arrives at my workplace is given a paper document that in big, bold letters says not to use the C: drive (the storage area on the local computer) and to use the networked F: drive instead. The advantages are many but too obscure to detail here (you don't have an F: drive mom, don't even start). Inevitably this document is never read and all sorts of important stuff starts accumulating on the C: drive.
Because employees fall from the sky around here with, typically, less than 24 hours notice that they're coming, they nearly always end up with temporary computers. Once their "real" computers arrive I get to see whether or not the shiny new penny actually has a brain between their ears. If I find stuff on the C: drive (assuming I bother to look), it's LART time.
Now, I'm not that nasty. I basically just move all their files to the F: drive where they're supposed to go. Of course, I leave the C: drive on the new computer empty, so when the "luser" comes back "oh my god! All my files are gone!". That's the LART. Usually one good scare is all it takes to get them using the F: drive.
I have other LARTs. If Kathryn is still reading this she probably knows of one or two, if only through stories (Kathryn is the only person in this entire flying circus that deserves the term hacker in the purest sense. I don't have to LART Kathryn very much, usually only when she drives up some blind alley. There are others that I've simply never needed to LART. Too few, unfortunately.)
My brother's LARTs are far less subtle, but probably more effective. Fortunately for his users he isn't in a position to regularly enforce them (he once made one lady cry though). To this day he rants that I mollycoddle my users. Sometimes I think he's probably right.
Of course, the most satisfying times are when users LART themselves. People who insist on using Outlook and then mail viruses to everyone in their address book, folks that start using the C: drive again and have a failure eat all their files, people that don't save their work, etc.
Do I know everything? Oh good god no! I'm basically writing this to avoid trying to figure out sendmail. I'm quite famous for rushing where angels fear to tread, and have more than once ruined otherwise happy, stable systems by tinkering with them one time too many.