I'm no expert, but from what I've learned as I study and research the power train in the current model Prius, towing with the front wheels on the ground is just not okay. The transaxle behaves like a CVT with two power sources and the potential (sorry, pun) for energy to flow in and out of the electrical system. Excessive over-run (towing) with the management system off could well damage the transmission.
I would be curious to try towing the Prius in Neutral somehow, but I just don't know enough to be sure how to keep the transaxle disengaged in Neutral without cycling the ICE or otherwise confusing the electronics. Still, I suspect it can be done.
Of course, there are those amongst us who would say -- Eureka! The Prius can be towed behind the behemoth motorhome or RV to generate (or regenerate power) as a piggy-back device! Why not tow two or three Prii behind your Winnebago and let them collectively push the 'bago like a team of sled dogs until their batteries are exhausted and replenish themselves by assisting the braking and downhill coasting ... it could be done ...
And seriously, given the flat-line sales of RVs since gas prices hiked, I have to imagine the big donk makers are working with the land yacht companies to incorporate bus technology and hybrid drive systems so that we will see RVs capable of SUV mpg. I'd like to see an RV running a bunch of "side wheel" (a term from Jeep referring to not four-wheel or all-wheel vehicles, but vehicles where each wheel has its own power source by its side) motors, with regenerative braking, loads of batteries and hybrid diesel-electric drive. I'd seriously enjoy my retirement touring around in one of those giant RVs and happily cruising at 45mpg ... with electric reserves that would allow me to run a kitchen, lights, hot water etc. for days without starting a generator ...
... imagine how many PV cells it would take to cover the roof of an RV ...
