A specific form of disappointment, wherein something that seemed so amazing and wonderful for so long finished with a stink that stains the whole previous positive experience.
Reference the reboot of Battlestar Galactica (BSG) being so flawless until it dwindled into an embarrassing conclusion.
BSG upset etymologically related to shorthand "v. upset" as in very upset, or "v.g." as in very good.
If Kate is chosen to be the One to Replace Jacob on LOST, I will be BSG upset!
I thought that guy was totally my soulmate until I found out he was super super gay and I was his beard. I am BSG upset.