This came up today and is an actual dilemma for me and a lot of other people, apparently. We haven't had problems but a lot of other people have and a friend asked about it. In rural areas especially, mail theft is a big problem at times [as well as mailbox smashing]. Some people opt to put in a mailbox like a tank mounted on the Rock of Gibralter. But the problem is that these are not legal. Only US Postal approved boxes may be used, and more importantly, they are supposed to be a breakaway design to prevent serious injuries if hit by a car - they are sitting right along the road so they do pose a hazard. Now it seems that no one really enforces any laws here as long the box meets the postal code, but by putting in a bullet-proof box, you are potentially putting others at risk and could be held liable if the worst happens. However, that is reeeeeeeeeeeeeeally unlikely. What is far more likely by probably many orders of magnitude, is mail theft. Would you leave your mail at risk, or take a chance that the long odds of an accident will never catch you.