You're trusting a lot more than Google. You're trusting unknown parties from your future who will be able to get subpoenas against you if they wish, should you ever inadvertently get into certain types of relationships with such as yet unknown parties.
Google is not the average person's enemy. If you are cheating on your wife, you don't want her to be able to open up your netbook and read all your emails about it. But if Google knows, it really doesn't matter -- Google is not your wife. Google could care less who you are sleeping with.
We actually don't know what Google cares about, nor do we (including you) know what Future Google cares about.
But your point is moot, because whether Google cares or not is irrelevant, if someone else gets a subpoena and Google hands out the keys and the data, which is conveniently backed up in the cloud.
Privacy isn't about doing things wrong and getting away with them.
If that's your rhetoric, why should my wife not have every right to catch me cheating? Privacy must be a terrible thing only useful to terrorists and adulterers, right?
Just be careful when you are defending something like this. I like my private life to be private, even when I'm not at a strip club.