My biggest concerns about truck tanks or gas cans is that I've seen some really poor practices, some of which are flat out dangerous--and yet there's no reason for these unsafe shortcuts:
Failing to ground the airplane or the cans/truck to the airplane;
Wearing nylon jackets while refueling;
Smoking while refueling (hard to believe);
Refilling cans while they're in the back of a pickup;
Talking on a cellphone or hand-held while refueling.
Since I can't burn mogas in mine (the STC for mogas and the STC for my engine don't match), I don't worry about these issues much, but I do refuel from self-serve, and I've seen similar poor practices from pilots who either don't care or who haven't been taught the need to do things like ground their airplanes, and ground between fuel trucks and the airplane, etc. I've even had to remind ramp rabbits to run the ground wire to my airplane.
I've never had to refuel my boat from a can. But I did add an extra tank to my boat, and I have the ability to run from extra boat cans, for extra long distance cruising. I did all that in preparation for my boat trip back in 2011, which you can read about in
The Ultimate Small Boat Adventure (still available, only $15.95, from Amazon, Barnes & Noble, etc.

). But I was very careful to do the entire extra tank installation using CG-approved pieces and parts, and I'm oh so careful with gasoline.
I'm sure I could think of other situations, but the point is that gasoline, whether mogas, avgas, boat gas, or even diesel fuel, can be dangerous, and some folks treat it like it isn't. As the wag says, half a boom will spoil your whole day!
Cary