I wish there was a gmail plugin that would make the users email publicly accessible, but read only. This would clearly test their "I have nothing to hide" argument.
There is a huge difference between refusing to have a lock on your front door and being okay with advertising to pay for a free service.
There is also a huge difference between publicly broadcasting your email and only the government having access to it.
Here's a hint: The NSA is not the general public.
(This comment should absolutely not be construed as acceptance of spying)