Information retaining to the content you write and who you follow is one thing, but spying on activity on your computer (like facebook is doing via cookies. That you are denied access if you dont allowe) and looking at who and when you comment on what and at what times you use the site is another thing.

And more functions and ways to show them who you are becomes more ways to controll you. Groups do , yes, add a god way to get personalised content. But that is also done via looking up articles by category and tags that already exist.

But this is my opinion.