we don't have an elf - i think it's sounds really fun, although hubby doesn't get it, will have to work on him for next year!! - but i have a friend who does. so far he has spelled his name out on the kitchen floor with cheerios (this was on the night he arrived), covered himself in the girls' hair clips, got into the fridge, unrolled a toilet roll all over the living room, brought them a magnetic nativity scene, complete with icing sugar 'snow' on the worktop, tried to climb into the fish tank, and covered the christmas tree in the kids' underpants!!! she is posting a pic on facebook every day showing what he is up to, and i have to say i think she is enjoying it at least as much as the kids! lol!
however, i clicked on the link posted above and i think the 'elf on the shelf' advert is creepy - 'the elf on the shelf is watching you, everything you say, everything you do' ?!?!?!?!