awd flatbed only!!! a rwd can be towed from the rear safely though, but even so, a flat bed is always best... unless the guy doesn't chain it well... had a few cars fall off the beds every now & again...
worse case I know of was a customer with an m3, calls bmw roadside, they send out a third party flatbed that then procedes to drop the m3 off the truck while moving... hits a parked car with it & everything, then re hooks it & brings it in to bmw... bmw didn't want to know anything, they said hey take it up with the tow truck... even bmw of north america washed there hands of it saying it was an independant, don't matter that they were contracted by a bmw dealer, and that it was a bmw roadside asistance call, still in litigation that one, I fixed the M3 though