Untagger
Someone who untags themself from a photo on facebook because they dont like the photo or dont want to be seen with the other people in the photo.
Tom is such an Untagger, he totally untagged himself from that photo from the party I posted on facebook.
untaggable
When you try to tag someone on Facebook but their name does not appear in the tagged photo and/or status post. This person may have opted out of being tagged in anything due to the increasing fear that unwanted friends, enemies, insurance agents and employers or prospective employers might see something they wish to keep private.
I tried to tag Sam and the two sisters but Facebook wouldn't let me. I guess they're untaggable.