I'd suggest keeping all of them as nofollow. Although they may benefit your rankings or your link profile, Google can easily consider it as spam and penalize you for that.
Refer to:
http://www.youtube.com/watch?feature=player_embedded&v=mTjN9x-by-I
The best option if the site is a good site, is to just keep one link on one page. That is if you really must.