With like buttons and social plug-ins strewn across more than 100,000 sites, Facebook is rapidly gaining power to track how its nearly 500 million users move across the web. The company says it focuses on high-quality interaction such as "likes" or comments on content, but what about all of the passive browsing data the company now has access to?
It's anonymized after 90 days, said the company's director of product Bret Taylor. That's a firm deadline, unlike a month ago when Ethan Beard, the company's director of its development network, said the data was technically logged at a base level but wasn't kept for very long. (He didn't know exactly how long.)
The data isn't anonymized immediately in part because the company tracks a "like-through" rate on all content, or how often content is "liked" out of all of the times it is exposed.
Every time you see a "like" button, a social plug-in or a fan box widget and you're logged into the social network, that embedded object makes a call back to Facebook to load your content. That in turn gives the company data on sites you visit even if you haven't clicked anything. It's not necessarily a new ability for Facebook; the company has long had widgets that show a property's fans and operate in a similar way, but they will be nowhere near as widely distributed as its like buttons over the next few years.
In general, tracking like this isn't new either. Cookies have been used to record what sites people visit and to serve them ads for more than a decade. But Facebook's power is potentially an order of magnitude stronger since your visitation data is explicitly tied to your real online profile and connections to real friends.
Google also tracks hundreds of millions of users, but for years it wrestled with the idea of even using a cookie in its AdSense network. The company has also built opt-outs for people to avoid interest-targeted advertising and recently launched a way for people to opt-out of being tracked by analytics. (Facebook hasn't done anything comparable to either of these initiatives.)