While you're thinking about the security of your email in the cloud, remember this: ANY of your email older than six months can be legally obtained by any U.S. law enforcement agency without any warrant or judicial oversight of any sort, even if you enable Google's new 46-factor authentication and use passwords that take minutes to type in.
http://www.wired.com/threatlevel/2011/10/ecpa-turns-twenty-f...
Do you have any passwords in your email older than six months? Any account numbers? Anything... incriminating or embarrassing?