I really wish this trope would die already. Google is not a person. Google does not read your emails. Employees at Google aren't sitting there reading your emails. An algorithm scans your emails for certain keywords, and displays ads based off of what it finds. That is not the same thing as reading your emails, and it's ridiculous that a forum like this would fall for such fear mongering.
Well, except when they do. http://gawker.com/5637234/gcreep-google-engineer-stalked-tee...
> An algorithm scans your emails for certain keywords, and displays ads based off of what it finds
It's more than that. For example, they also scan images to identify child porn. Or Google Buzz, which showed that they scan and track the people you contact most often, and may do undesirable things with that information, like publish it.
It's naive to expect that Google/Facebook/whatever supplier of corporate IT stuff will just serve as a wholly passive platform, especially if the service is not paid.
I was trying to point out that some level of snooping by the cloud providers themselves is going on right now. Note that I tried to defend Google's behavior by saying that it is no secret and people are opting into it willfully.
Yes, they scan your emails. But not _particularly_.