- Theft: A thief might pick up the entire box and carry it away to pry open later.
- Fire: Though manufactured to resist high heat, the box should be kept where it is least likely to succumb to fire/heat. The best places are lodged in cement, like in your basement or garage floor or walls.
- Earthquake, flood and other disasters: Many boxes are designed to endure one or two dangers not multiple like say a fire and a flood.
Safe deposit boxes are not covered by deposit insurance. The FDIC and NCUA do not provide insurance for the items in your safe deposit box. Your home owner's insurance also does not cover your safe deposit box. You can insure these items, however, you'll need to discuss that with your insurance agent.
Home boxes are covered by your home owner's policy since they reside in your home.
Be careful about what you put into a safe deposit box. Do not place your original will in a safety deposit box. State vary on laws regarding who can access the box. In Colorado, if you should die only a named beneficiary may open the box upon your death. (Unless the State has reason to access.)
Also don't put in documents that you need to access frequently or in a moments notice, since you'll have to wait until the credit union or bank is open for access.
At least one article that I read on this topic claimed that a safe deposit box is cheaper than a good home box in the long run. I still don't know about that. But I do know that the little box I keep in my home office isn't worth a dang.