Originally Posted by WhyFi

If given a link, yes - one can view it... but finding an activity without a link, without the benefit of scrolling though a user's profile, or without a FlyBy, is... well, it's not impossible, but it's certainly more effort than most would be willing to invest. Maybe they could guess that you traversed a given segment and, if they're a paying Strava member, they could view the daily leaderboard for a link to your activity? I mean, no offense, but ain't no one interested enough in me or you to jump through those hoops.