Do you even know what you originally replied to? Because it's right there. We already know Google stores a great big swath of data about you for various purposes, including advertising. We know that one of the many sources of this data is what is gleamed from scanning emails for advertisements. Don't act like it's not common knowledge.

Yes - it is common knowledge that Google (and others) use email for advertising.

But you (or perhaps upthread) are implying that Google willingly hands over data to government authorities.

The evidence would point to the contrary: Google (and Microsoft I might add) are complying with the law, but are not simply rolling over and handing out whatever is asked of them.

Their ability to fight back against unwarranted requests is probably much better than someone running their own mail server in their basement.