I have a hard time believing that.
Email retention is a no brainer...
And security guarantees are an absolute requirement for ANYONE.
Heck, I know for a fact that Google is doing this for government entities, and they have a HUGE email retention requirement.
Business email, documents, and intranet sites for Government ? Google Apps
They only guarantee 3 nine's. I work in a 5 9's shop. So, it's a no-brainer: We can't use Google Apps for email, since we have a 5 9's SLA.
Email retention in a Google App environment is still handled in-house through proxy appliances. There is no way to mandate inside of Google Apps a retention policy. It's a third-party solution.
So, if you doubt it, please, contact a Google Sales rep, and have them set you up with a project manager to discuss it.
And, yes, they are FISMA compliant, but that does nothing to answer the question of: "If we change our solution, how do we get our email back". Our email being the corporation's email. Also known as our "Intellectual Property".
Again, if you doubt anything I say, feel free to contact the Google Sales office, and get set up with a project manager. He/she will be able to discuss the in's-and-out's of a cloud-based email solution.
And, I'm not sure you are really aware of the varying levels of security out there: FISMA, Visa PCI, FIPS-2, SAS70, etc. Unless a solution is certified to the varying levels out there, it can not be used for various services (ie, if it's not Visa PCI and SAS70 certified, you can't use it if your company accepts credit cards; if it doesn't meet FIPS-2, then no Treasury or Dept of Education data; etc).
I'm confused as to why you are comparing the public Gmail to the Corporate Gmail?
Corporate Gmail only offers 3 9's. It's pretty much the same level of service you get with GMail.
But, as I've said a few times here, feel free to contact Google Sales, and have a project manager meet with you. I've been that route, and made the decision for my company already to stay with Exchange in-house.