It surprised me that only 10% of his random (French) sample is active daily (179/1751=10%). In my contacts, I do see people who have accounts but haven't used it in weeks, but it's not the norm. However, I see lots of people in my contacts who show no info for Last Seen. Is he underestimating how often people configure the privacy setting for Last Seen? Or perhaps there is another factor that determines when Last Seen gets shown?