Google will track users' activities across all its services
More here: Google Expands Tracking on Sites - WSJ.com
In a controversial move, Google Inc. said it will track users' activities across nearly all of its services, and that in many cases, users can't opt out of the tracking.
It's not entirely clear how the company will use the information. But it could mean that when users search via Google, the company will use their activities on sister sites like Gmail and YouTube to influence those users' search results. Google hasn't done that before.