The change was announced in a blog post today and will go into effect March 1. What it means is that if you are signed into your Google Account to use any service at all, it can and use that information on other services. As Google puts it:
What this means for you is that data from the things you search for, the emails you send, the places you look up on Google Maps, the videos you watch in YouTube, the discussions you have on Google+ will all be collected in one place. It seems like it will particularly affect Android users, whose real-time location could be up for grabs. And if you have signed up for Google+, odds are the company even knows your real name, as it still places hurdles in front of using a pseudonym, although it no longer explicitly requires users to go by their real names.
All of that data history will now be explicitly cross-referenced. Although it refers to providing users a better experience (read: more highly tailored results), presumably it is so that Google can deliver more highly targeted ads. (There has, incidentally, never been a better time to familiarise yourself with Google's Ad Preferences.)
So why are we calling this evil? Because Google changed the rules that it defined itself.
Google's philosophy speaks directly to making money without doing evil. And it is very explicit in calling out advertising in the section on "evil". But while it emphasizes that ads should be relevant, obvious and "not flashy", what seems to have been forgotten is a respect for its users privacy and established practices.
Among its privacy principles, number four notes:
People have different privacy concerns and needs. To best serve the full range of our users, Google strives to offer them meaningful and fine-grained choices over the use of their personal information. We believe personal information should not be held hostage and we are committed to building products that let users export their personal information to other services. We don‘t sell users' personal information.
And much worse, it is an explicit reversal of its previous policies. As Google noted in 2009:
Previously, we only offered Personalized Search for signed-in users, and only when they had Web History enabled on their Google Accounts. What we're doing today is expanding Personalized Search so that we can provide it to signed-out users as well. This addition enables us to customize search results for you based upon 180 days of search activity linked to an anonymous cookie in your browser. It's completely separate from your Google Account and Web History (which are only available to signed-in users). You'll know when we customize results because a "View customizations" link will appear on the top right of the search results page. Clicking the link will let you see how we've customized your results and also let you turn off this type of customization.
The changes come shortly after Google revamped its search results to include social results it called Search plus Your World. Although that move has drawn heavy criticism from all over the web, at least it gives users the option to not participate.