Then I suppose getting a thank you is out of the question for making you aware that other "only name and password" services like Disqus really do much more than what you realized. You had no idea at all but you should have.
IMO Google is among the most transparent of all the techs when it comes to disclosure. Perfect? Hardly. That old "don't be evil" meme outlived it's usefulness a long time ago. Everyone knows Google makes most of it's money from advertising and a lot of folks consider that wrong for whatever reason. But at least in their quest to be the best in their industry they seem to keep whatever they mine in their own custody and control, and put the user privacy disclosures and controls all in one place instead of trying to hide it. and hope no one goes looking.
"they all do it" is no defense or excuse.
on a scale of 1 to 10 (not counting the NSA), Google scores the 10 for maximum data mining of its hundreds of millions (billions?) of users in so many ways. you're right, we don't really know what MS is mining from its built in Windows OS "back door," and i'm sure it copies Google's practices as much as it can with all its ecosystem services, so we can't really score them, but MS could be a 10 too. they just aren't as good at monetizing it.
none of the others have the same massively wide scope of opportunities as those two. Facebook and Amazon and Yahoo i'm sure mine everything possible from their lesser ecosystems - let's give them a 7. god only knows what Samsung is doing - it's Korea - but their ecosystem is small, so a 4 is probably the most they can manage from their Android overlays and smart gadgets (not counting their world-leading industrial espionage). Websites like Yelp and many others mine as much as they can from whatever we use them for, so give them a 3. Apple limits its mining to its various stores and whatever else you opt-in to, so call it a 2 - the most self-restrained of all the big guys.
but "they all do it" is just no exculpation. and Google's limited "transparency" about its doings is just a fig leaf for suckers.