Which cup is mine?

It seems to be an epic battle at all social gatherings. A hundred cups, one color, one design. Which one was mine? Do I dare drink out of the one I think is mine or pour myself a new one? Solutions range from permanent markers to decal labels or ornate glass tags. So why hasn't anyone just put together an assorted set? These guys did and they are awesome. Subtle brilliance. I love it but am still experiencing that twinge of jealousy that comes from not being able to have thought this one up on my own.