I'm a bit cranky with Strava at the moment. The local leaderboards were getting a bit dramatic, so I decided to quit them. In the past, one could do this while keeping activities public; at some point, they changed the settings so that the only way to opt-out of leaderboards is to set activities so that they are either visible only to followers or private.
Both of these settings also preclude one from participating in challenges, so I will not be getting a cool T-shirt or those Rapha patches.