Here’s another reason, if you needed one, to forego snail mail. Forget the latency and cost; it turns out that the USPS takes pictures of both sides of every envelope they process. This is analogous to the NSA’s wholesale collection of phone metadata in case it may prove useful sometime in the future.
Of course, even if you use encrypted email, the government is undoubtedly collecting similar metadata. The FBI is always whining about how the switch to digital communications is making their wire tapping sources “go dark.” News like this story make you glad.