Also, for criminal matters law enforcement has been able to obtain search history from Google with a search warrant. So they have the ability to search search history, which is a dataset several orders of magnitude larger in size & scope than GMail.
If you seriously believe that Google doesn't have the capability to perform discovery on the public facing GMail, that's fine, but the capabilities that Google has in production today suggest that your belief is not quite correct.
But again, Google offers a similar functionality to enterprise Google Apps customers: Google Vault. (https://support.google.com/vault/answer/2462365?hl=en)
Also, for criminal matters law enforcement has been able to obtain search history from Google with a search warrant. So they have the ability to search search history, which is a dataset several orders of magnitude larger in size & scope than GMail.
If you seriously believe that Google doesn't have the capability to perform discovery on the public facing GMail, that's fine, but the capabilities that Google has in production today suggest that your belief is not quite correct.