hedwards: Of course it's exploitive, to some extent all sales are. The ones they've been running though are far worse than anything I've seen elsewhere. Expecting people to take off from work and not sleep for the Insomnia and time machine sales was ridiculous.
Personally I thought Insomnia was fantastic. It was also very effective at draining my wallet, but fortunately coincided with my birthday.
Considering they run "normal" sales nearly every weekend and often during the week, it seems a bit ...myopic, perhaps...to call them out for doing something different with 3-5% of the days in the year, even if some of those experiments don't work, or at least don't work for a particular individual.
I don't have the inclination for gambling to participate in the Pinata as designed, but I don't think they suck for attempting it, since they'll almost certainly be back to 'normal' sales soon after this one ends. And as some of the jokes above note, we're not coerced or forced into participating, are we?