Text (UG+errata): 2/2. ; ~this~ comes into play with one +1/+1 counter on it for each game you have lost to your opponent since you last won a Magic game against him or her. [Oracle 2009/07/08]
"Lost" only counts games of Magic. [QAS 1998/09/09]
In tournament play, only games in that tournament count. [QAS 1998/09/09]
Gus is not a Legend since there is no one Gus. Gus is everywhere. [QAS 1998/09/09]
In a multi-player game, choose a player when this comes into play. [D'Angelo 1998/11/09]
Optional Rule: "Lost" means any sort of loss - losing a bet, losing a poker game, etc. [Barclay 1998/08/13]
All tournament formats have banned cards from Unglued.