Spotted at the Edinburgh Interactive Festival in a playable demo of Epic Games' PLAYSTATION 3 version of Unreal Tournament III, the Gamercard is presumed by the eagle-eyed staff at Games Digest to be the johnny come lately equivalent to the Xbox 360's Gamertag. The "Oops, you shouldn't have seen that" feature is reported to be accessed via the SIXAXIS triangle button but is unfortunately thin on details.
Could the Gamercard be a facet of the just announced agreement with GameSpy to license its tech? Such a thing sounds not too dissimilar from the Gamespy "Sake" system. Or is it the "Atlas" feature? Regardless of the implementation, I'm sure we'll be hearing more about the mysterious Gamercard soon.