There is, of course, an option to keep your profile un-sharable; find that in the app's Discovery Settings.

Ostensibly, this is all so you can show your friends people they might be into, though surely it'll be used to gossip about all of the surprising folks you see on Tinder -- like Lindsey Lohan, Katy Perry or Ashton Kutcher, for example. That said, this may be a good time for people who shouldn't be on Tinder to update their privacy settings (or delete the app for good, you right-swiping scoundrels).