I'm guessing it's something like one person brings a stroller, then hands it off to another (or leaves it at the bell desk) for another to use on their trip, who then leaves it for another... It's a nice idea, but you have to have a stroller to start it, and a good record-keeping trail to figure out where it goes and who it gets left for next. I think Disneydaz has some sort of mini-fridge swap at WDW.