[HerraBRE]

To expand on this slightly, and illustrate:

I'm going to go out on a limb, and assert that THE most common attack performed against peoples' e-mail, is a jealous person who knows their partner's password logging on to their e-mail and reading their mail.

I know people who have done this. You probably do too.

People trust each other, people routinely tell their loved ones their passwords. And relationships routinely fall apart and trust is routinely violated.

Deleting from the server mitigates this problem and greatly reduces the window of opportunity for the attacker.

The privacy cost/benefit ratio for routinely deleting from the server probably beats every other privacy enhancing technique out there. Super simple, super effective.

Techies too often forget that privacy isn't just about the NSA, APTs and TLAs. The fact is, the people most interested in violating your privacy are the people who know you personally...