well, some impressions from Germany:
obviously due to the heavy increase of eBay transfers there are frequent openings of letters which look valueable, like 'personal delivery' etc. This happens inside the postal service as those letters are closed again after the content been taken, which makes it very difficult to proof the fraud.
In areas of the city with a majority of wealthy inhabitants public boxes for outgoing mail are systematically emptied in the hope someone sends cash in a letter.
When we used Apple packages to send service parts those were frequently opened to peek inside. Since they never found a Mac the stuff always arrived...
If I have something valuable to send, I always reuse some shabby envelope, hand-written and not even completely closed
cheers, Tom