Before it explodes quoting from the post: "It's important to remember that no one else can see your Activity Log, including your search activity"
FWIW I've flagged this, as it's really now HN worthy IMO or at the very least shouldn't have a sensational/link bating title like this.
It is obvious that Facebook has this data, Google has your search history, a telecom has your call logs, and an ISP might have your web browsing history. However, even making it available to the user themselves opens them up for accidental or socially pressured privacy invasion.