For instance they'll see what emails you receive and subscribe to, what videos you watch, what things you search for, what sorts of documents you work on and what the content of those documents is, what you blog about, what you take photographs of and where, what newspapers and blogs you read, what you buy online, what parts of the world you're interested in (and where you live), who you chat to and what you like to buy.
All of this information, when put together, helps advertisers paint an incredibly detailed picture of you and with about a billion users worldwide, that information is incredibly valuable.
Now Microsoft have hit back with newspaper adverts in the US saying that this isn't what want at all and that you should 'obviously' use their products and services instead.
In the advert they say...
Google is in the process of making some unpopular changes to some of their most popular products. Those changes, cloaked in language like "transparency", "simplicity" and "consistency" are really about one thing: making it easier for Google to connect the dots between everything you search, send, say or stream while using one of their services.
But, the way they are doing it is making it harder for you to maintain control of your personal information. Why are they so interested in doing this that they would risk this kind of backlash? One logical reason: Every data point they collect and connect to you increases how valuable you are to an advertiser.
So is this fair enough, sour grapes or the pot calling the kettle black? In fairness it is all of the above as there are elements of all of these in the advert. Google make almost all of their revenue from advertising and the better and more attractive they can make their own advertising, and the data they collect on their users, the more companies they will attract and the more money they can charge for the (your) personal information.
Many people simply don't want to be tracked and Microsoft point out that you can do this in the latest version of Internet Explorer. What they don't mention is that you can also do it the latest version of Google's Chrome browser as well and that many of the advertising and data-mining tactics used by Google are also used by Microsoft.
Consumers will have to decide for themselves how they feel about the approach Microsoft are taking here, though many will just see it as a company taking advantage of an open goal for a publicity stunt. The fact remains though that the US Congress is so concerned about the new changes Google is introducing that they are holding an closed door hearing to discuss what the changes mean.
Ghacks is a technology news blog that was founded in 2005 by Martin Brinkmann. It has since then become one of the most popular tech news sites on the Internet with five authors and regular contributions from freelance writers.