Comment Headache for diagnostic tests (Score 2, Insightful) 660
I'm surprised nobody brought up -- needless encryption makes a *huge* headache for running diagnostics on any sort of server. If any sort of script is not working, there is difficulty in evaluating what is happening, and even network diagnostics is much more complicated.
Additionally, encryption wastes a lot of CPU cycles if not needed. Although a small argument, this slows down networks and costs $$$ by burning fuel.
Finally, you have to make sure encryption is done right to be secure. If you encrypt everything, it is more difficult to see where there might be a vulnerability because there is more to audit. Think of the analoy to personal encryption -- unless you work for the NSA or something it is much better / easier to encrypt a directory on your disk with personal stuff than trying to encrypt your whole logical volume.
Which would be easier to recover from if you had a hardware fault / disaster?