Untagonised 

The action of being so disgusted by a facebook photo that you untag yourself from it in the hope that nobody will see it.

That photo you posted last night really untagonised me. You should ask before posting stuff like that up!

Untagonised by dotmit August 5, 2010

untagonist 

untag + antagonist

one who untags unflattering pictures of themselves on facebook

Amy and Zoe posted those pictures from last night, and I turned into such an untagonist!

untagonist by a+z4evamo April 7, 2009

Untagonistic 

Your right to refuse to "untag" an obnoxious photo at the demands of a Facebook friend.

Robyn: WHY didn't you untag me in that photo of me sleeping on the bathroom mat?
Mike: Because I was being untagonistic...

Untagonistic by Consumer Dejour May 10, 2011