If you follow other users their activity is displayed in your news feed, i'm not sure what else - I just watched this thread, so I assume any updates to this will also appear in my news feed? But we shall see.
Edit: Ok, watched threads and threads you've interacted with don't appear... only your followers interactions.
It's a social connection. You can either stalk someone who doesn't like you and you just can't let them go, or you can use it for what it is intended, follow a person you consider a friend, who probably likes you back. And you can keep track of what you're doing (what you would otherwise let eachother know at the end of the day in a bar over a beer ..)