Cheeze is right... when you turn on the tracking... it starts when you start it. So if you start it at home... your friends will see where your home is. As for adding friends... you have to search by name and then it sends a confirmation to that person for confirmation. So you won't have random friends. The point still remains... your routes are available for others to see.
The app also allows you to track data (distance, time, max & avg speed, as well as post photos, like, and comment. Not much different than a running app used to track exercise.