Thanks for the suggestions Ewan.
The privacy zones one has come up before and in response to this we introduced the Delete Homestretch feature, which makes it easy to remove the first and last section of the route leading up to your house.
I've added your other suggestion of allowing routes to be saved as "Unlisted" to our Feature Requests list (number 67) so anyome who is interested in this can vote for it there.
At the moment You have 2 options, Public and Private. Would it be possible to add a third option (similar to youtube video share) where it is unlisted and you can still share with a direct link, but the route is unlisted in the search.
Second suggestion is something Strava do and that is have privacy Zones, alot of my routes are from my home or Work ... Strava blanks out any areas marked as private from your route.However there handling of that is somwehat awkward with just an open space where your privacy zone is ... Making it kind of obvious.You could easily have the route terminate elsewhere or loop past your privacy zone so its a little less obvious!