To start, Facebook tends to store browsing data by scattering it to the four winds: the site, your personal ID and the time of visitation are in different places. And when Facebook stores that data based on date and time instead of individual users, it can't easily associate history with specific people. The social network had to craft a user-focused data storage system just to make Clear History feasible.

This isn't going to help Facebook's image when it's already grappling with privacy bugs that have exposed data for millions of people. One of its marquee features from this year's F8 might not show up until a full year later. Facebook is at least confirming that Clear History is on track, though, and it now has a more definitive timetable.