While in many cases forums will use and love the feature I know many people will feel uncomfortable with it. I can just hear the complaints of Big Brother (not the TV show) and 1984 etc etc. Users will need to have the option and selecting if they can be followed or not. I would really really like the option in the Admin area of being able to turn it off and set a default for new users.
I can see where you were trying to go with this feature but I'm not sure its the kind of thing that every site can (and will want to) use.