What is living on this tree

Can anyone let me know what is wrong with this oak tree at my work place? The entire tree is covered with these "balls".

 

Agrobacterium tumefaciens perhaps?
http://eol.org/pages/976308/overview

 

Horned oak gall or something similar.

http://web.extension.illinois.edu/fjprw/downloads/5600.pdf

 

Thanks for the posts. Judging by the number of galls, this pin oak will not survive.

 

i'm not sure the oak will die .. i remember one summer, working in victoria, bc .. i was walking down a residential side street lined with oaks .. i kept hearing this quiet popping sound and when i looked for it, i looked down, and the street gutters were filled with these tiny little bouncing critters .. which i later found out were an oak gall of some kind .. which had left these 'nests' i suppose .. i believe those oaks are still there, years later ..