There seems to be much concern that the PB container will burst, but no one has posited the mechanism by which this could happen. (Afterthought: this type of PB often comes in thin PET containers with snap lids, not the sturdy jars with screw-on lids used by the likes of Jif or Peter Pan. They may well be crushed. )
The most likely occurrence, to me anyway, is incompletely mixed ground peanuts. Well mixed peanut pieces and oil appears unlikely using this method.
What's to fear? Shake away!!
So we have multiple failure modes consisting of:
1. Jar breakage.
2. Lid retention failure.
3. Inadequate mixing performance.
4. Mechanical failure of the shaker assembly.
5. Internal electrical failure of the shaker assembly.
6. Operator electrocution.
7. Operator dismemberment.
8. Operator decapitation.
9. Microbial contamination of product.
10. Incorrect ambient temperature.
Now, things could get interesting if multiple sequential failures were to occur. Granted, the probability matrix would likely indicate a low potential, but let's say 1 or 2, 3, 9 and 10 occurred, one could potentially release Anthrax into the environment, causing a massive, deadly epidemic.
Bottom line is I wouldn't touch it.