Interesting, have never heard of the "death wobble" with respect to a C-Max being towed (mostly I've heard it about pickup trucks and 4x4's on the highway).
Here is an example:
and here is a good discussion about it on irv2:
(From the looks of the discussion its just something that happens on slow, sharp turns and stops when you stop and straighten out--also can be addressed by a camber adjustment.)
I tow my C-Max Energi on a dolly so no "death wobble" for me. Love charging it up at campgrounds and doing a lot of my sightseeing in EV mode.
My parents had a 2009 Edge that they would tow around with their motorhome. As far as I know they never had an issue with it.