Yeah, but it essentially always happened. You know those warranty cards you get with new products? They have always been used to build marketing databases.
http://www.nytimes.com/2003/12/25/technology/do-you-really-n...
Meanwhile, no, you have no right to dictate how I contract out how I handle my mail by sending me a letter. You gave me that letter, and you'd have a difficult time making a case even if I then proceeded to make thousands of physical copies of it and distributed it at a street corner.
I guess what I'm saying is... what's your point?
edit:
You appear to be misreading your parent comment. The parallel situation they describe is precisely that the recipient engages a company to process their mail (read the description: "you hire some company to sort and collate your mail (and toss out your junk mail for you), and in exchange they slip in some coupons [for] people who get the kind of mail that you do". All of that applies to receiving mail, not sending it.)
And this is precisely what's happening with Google: if you send mail to my gmail address, I've engaged Google to process it on my behalf. You have no say in the matter, nor can you.
There's nothing implied in sending an email beyond "I want you to read the contents". If there's more I want you to do, those wishes would be in the email itself.
30 years ago, if I wrote a paper letter to a company, I was not implying that I want them to build up a profile of me based on my stated info compared to the stated info of other people, where my letter came from, type of stationary, quality of my grammar, etc., then send me coupons that match the behavior they expect of people of my profile. I am implying that I want them to read my letter and take care of my request.