buck rubs

does anyone actually know that a buck rub on a thicker tree was from a bigger buck? 

I watched a show on the outdoor channel last year. These guys said there was no rhyme or reason between the size of the rub and the buck that made it. They showed footage of lil buck rubbin out big trees and monsters rubbin on saplings.
 
BH

Tree size means nothing, I have a vid that I took last year on the first day of a tiny buck rubbing a tree that was at least 16" across. It's a cell phone vid and hard to see or I would try to post it. I always heard "the bigger the tree, the bigger the buck" when I was growing up, now I know better...

Like S-10 and SmMouth have stated, there is more to it than just some missing bark on a tree.  You need to be intuitive and look at the bigger picture.  Like mentioned, looking at things like how the bark is removed, and markings on adjecent brush/trees can both tell you an awful lot about the buck(s) behind the rub.  Additionally, IMO one of the easiest ways to determine a rough size of the deer making the rub is to look at the height of the rub. A 1.5YO spike simply can not rub trees to the same height as a 4.5YO 150" buck.
 
I run a pile of trail cameras and over the years I have captured lots of pictures over what I would consider to be big rubs.  From my experiences with the cameras, the bucks visiting the big rubs have generally been bigger bucks.  Some small bucks would visit the rubs, but they never exhibited the same amount of interest with working the rub as the big ones would.