On your profile page, click on the Activity Log:
In the Activity Log, there's an checkbox to show "Only Me" activity:
OH GOD NO
Our Facebook profiles are all about who we want to be, not who we actually are. Facebook offers enough controls to tailor what actually shows up on your profile and in your friends' newsfeed that most of us can get away with seeming like a half-decent human. But the search box knows our true nature.
The opposite of our manicured social profiles is search. Search is embarrassing. Search is what we use to find out what our weird rash is or to look for topless celebrity photos. Search is our horrible, gross humanity leering back at us.
On Facebook, the search box is what we use to stalk our exes or creepily keep up with a high school crush. Seeing who you've searched for on Facebook, right there on your activity log, is downright mortifying. The "Only Me" activity is like seeing the gnarled hideous portrait of Dorian Grey we've been hiding in our attic, while our public-profile selves have been posting our happy vacation and brunch photos agelessly.
The searches are "Only Me" by default, and clicking that button on your profile doesn't mean anyone else can see them. We should know by now not to feel shocked that Facebook knows whose profile we've looked at or that what we search for is stored in some server in a data center at the bottom of a volcano or something. Yet it's a surprise that this information is actually sitting there on your profile this whole time, visible if you want it.
While this information is private, imagine if someone had access to your account from your computer, which isn't a totally unreasonable circumstance. Young people even have a name for it: "frape," for Facebook rape, a term that isn't appropriate, but endures nonetheless. Of course, if someone is motivated to snoop through your Facebook account, it's between you and your priest what other horrors they might find in your inbox. Yet even those of us with a clean conscience would probably still feel like a huge creep when faced with our people-search history.
This feature has been around on Facebook for a while, but most people will be surprised it exists. I only discovered this while reading relationship advice on Reddit (I know, I know). A Redditor was troubled by information he found in his girlfriend's search logs when he snooped into her account. He discovered she had been repeatedly searching some other guy, though she didn't message or interact with him. Her guilt was in thoughts only.
Seeing your full activity log is a reminder that the mere act of using Facebook IS creepy. After a decade of being on social networks, we've normalized the weirdness of being able to pull up photos and information on all our acquaintances instantly. This is a stark reminder: We're all kind of creeps now.
UPDATE: A commenter points out that it's possible to erase all these saved searches all at once. Go into Activity log, and find Searches on the left column (you'll have to click "more" to find it), then there's a button to "Clear All Searches". Voilà! Here's more detailed instructions.