Google is consolidating it's Policies, and Facebook is continuing to roll out the new Timeline. Both developments could be seen as aiming to organize data better and so make things more convenient. Which sounds great, until you read things like:
"If you haven’t been keeping up with how Timeline will change your Facebook experience, then you are in for one heck of a surprise. As ReadWriteWeb so aptly states, “Timeline turns the profile into an illustrated, browsable history of a user’s entire life, with major milestones and little moments smartly chosen by Facebook’s algorithm.”
Prior to timeline, Facebook stalkers would have to manually sort through pages and pages of wall postings to find out the personal details of your Facebook activity. Timeline drastically simplifies this process."
From Facecrooks (a blog which monitors scams and nuisances that appear on Facebook)
"By combining the wealth of personal data it already holds, Google is enhancing its ability to run targeted ads which allows it to compete with Facebook, which already shows ads based on a users’ interaction with brands.
For example, the blog post says Google will now be able to “provide reminders that you’re going to be late for a meeting based on your location, your calendar and an understanding of what the traffic is like that day.”
Not all users will be comfortable letting Google take such control over their lives, despite its claims that it is trying to “help you by sharing more of your information.”
The theme is that better-organized data might not be "better" from the customers' point of view. Or at least might have a downside.
Apart from worrying about stalkers or Big Brother watching you, another hazard is the way that joining up the information can accidentally break down the Chinese walls that many people like to have in their lives. For example, Chris Nuttall, writing the in Financial Times, tasks of finding that his daughter is accidentally sending him a live feed of a photo shoot she was doing for a class project. Meanwhile, he's listening to Spotify and accidentally streaming a list of music he is hearing to his Facebook profile. ("Happily, I had been displaying my usual good taste in tunes, rather than indulging in the occasional guilty pleasures of 1970s prog rock."). Similarly, you could have your feed trumpeting "I just bought [insert item chosen for wife's birthday here] at Amazon". She might no longer be surprized.
An important thing here is that the need for privacy is contextual in a subtle way - you might usually be fine with Amazon boasting of your custom, but not for presents. You might be usually fine with your network knowing what music you are listening to, but not if you're kindly allowing your kid sister to use your computer and she's on a Hannah Montana binge. You might be fine with Facebook "knowing" you're gay (i.e. this being pretty easily inferred from your "likes" and posts) but you might prefer that to be none of your work colleagues' business.
Note added 29 Jan 2012: The Onion just covered much the same ground, but satirically: "Google Responds To Privacy Concerns With Unsettlingly Specific Apology"