I Feel Like An Idiot For Asking This...
 

But ... how do I turn social bookmarking on in certain forums?

I noticed in some forums I have it on and in others it doesn't appear.

So how do I turn it on in those forums that it doesn't appear?

Social bookmarking is only viewable in forums that have threads that are viewable by guests..... if guests can not see threads in a forum, then social bookmarks do not appear.

Reference: http://www.vbulletin.com/docs/html/m...al-bookmarking

Ah, thank you! Much appreciated!