I used to do recovery for the RAC on the transporter wagon and i can remember on one occassion my mate was on duty using the spec lift (A wagon that can do a rear or front end lift) anyway, he was driving back from a rescue and he saw that a car had broken down on the M4 by Magor, he pulled in and 3 lads got out the car and said thank god, we have ran out of petrol.
We used to carry 2 gallons of petrol and diesal for this type of call out, my mate (Nick) told them if they paid for the gallon of petrol he would let them have that, one guy said ok, well, as Nick was walking to his wagon one of the lads came up behind him and punched him to the ground then the other 2 lads got stuck in also. Nick ended up in hospital and most of his own tools etc were stolen from his wagon.
3 weeks later these lads were caught because that part of the motorway where they stopped was on camera, they each got 18 months inside.
From that day I have never stopped for anyone other than a lone female, I would love to stop to help others but in this day and age NO WAY.