is Cargo Theft Common?

It's a fact that almost all thefts of opportunity can be prevented just by using common sense. Of course if an organized gang is after a specific load, most likely they will get it.
One thing that has always bugged me, is the driver leaving his truck not only unsecured but running while he goes into the rest area head, to take a dump.
Might as well stick a sign in the window saying "PLEASE STEAL ME!"

This is undoubtedly one of the best ways of deterring someone who is an opportunist.

 

It happens. Best thing to do is keep a hefty lock on the back doors and maintain situational awareness. Look out for each other. When parked keep an eye out for suspicious persons who don't seem as though they belong in a truck stop. People who seem to be needlessly walking around the backs of the trailers are some to look for.