You should definitely not rel="nofollow" all outbound links. Do it to sites that have a risk of becoming a spam site maybe, but a quality site usually doesn't b

You should definitely not rel="nofollow" all outbound links. Do it to sites that have a risk of becoming a spam site maybe, but a quality site usually doesn't become a spam site overnight and you'll do more harm than good to yourself adding by rel="nofollow" to every single outbound link. Google wants you to link out to quality sites so you don't need to nofollow those.