Firstly, if you've uploaded that data to Strava (which you have if friends can see it), then a bug in the public view may expose it one day and there's nothing you can do to prevent that other than stop uploading to Strava, delete your data and hope they really delete it and don't just set a facebook-style "deleted" flag.
Secondly, the public can't see my starting point from my tracker - its data simply isn't uploaded to the internet - but because my address is a matter of public record for other reasons, I have several types of locks and alarms guiding the bike shed. In this borough, most houses probably have some bikes (not all ridden, of course) and there are many others which will be easier, richer pickings than mine. Especially if a Strava bug ever exposes where all the fast bikes live