recent trends in internet applications have made activity data a part of the production data pipeline used directly in site features. These uses include (1) search relevance, (2) recommendations which may be driven by item popularity or co- occurrence in the activity stream, (3) ad targeting and reporting, and (4) security applications that protect against abusive behaviors such as spam or unauthorized data scraping, and (5) newsfeed features that aggregate user status updates or actions for their “friends” or “connections” to read.