There are two bands called Stag. Stag are an Alternative/Indie rock band from Manchester, United Kingdom. Another is a boring two piece black metal/sludge band from Columbia, MO that for some stupid reason refuses to die.
There is at least one artist (see below) whose works are sometimes tagged as "2". If this "artist" appears in your charts and is not the music of that artist, do last.fm and yourself a favor. Fix your tags by putting the actual artist name in the artist field. ----- Tracks by 2, The Ranting Gryphon (such as "Coyena", "March of Doom", "Salvation", and "The Pawpet Song") are sometimes tagged as simply "2".