[chandler]

Let's disregard the blackmail aspect of nothing-to-hide.

Consider that lobbyists & bureaucrats now have the capability (prevented only by policy) to snoop the past and present communications of elected officials.

Imagine your squeaky clean politician, whose friends are equally squeaky clean. How effective will this politician be when at negotiations, hearings, etc, his opponents have already studied his history and relationships? They know where he likes to eat, where he's been on vacation, where his dog goes to the vet. They know how the talks are going, they know which strategies are working, and which lines of thought aren't.

In short, they know which ideas to push, and which ideas to back away from.

This politician will be both ineffective at representing his constituents, as well as unable to point to why this is the case. And he's never going to cry out "blackmail!"