Facebook demetricator by Benjamin Grosser:

Demetricator is free software that runs within the web browser, constantly watching Facebook when it’s loaded and removing the metrics wherever they occur. This is true not only of those counts that show up on the user’s first visit, but also of anything that gets dynamically inserted into the interface over time. The demetrication is not a brute-force removal of all numbers within the site, but is instead a targeted operation that focuses on only those places where Facebook has chosen to reveal a count from their database. Thus numbers a user writes into their status, their times for an event, etc. are not removed.