Criminals are using it.
High fives to the folks at research in motion, the makers of the blackberry. Now everyone can have military grade encryption on their messages. Of course this makes tapping into those blackberries by police/intel types more difficult. This in turn has prompted mp's in canada to attempt to introduce legislation that would force rim to make their software tappable. Can't see that little plan going anywhere fast.
Blackberry has a easy-to-read 92 page document outlining their security systems here (in case you have nothing else to do for the next 2 hours or so).