Billboard magazine has chosen the end of the 2000s to name not just their top cts of the year, but of the decade. I won’t pick nits (the decade actually began Jan. 1, 2001, not 2000 — a common but annoying mistake), just pass along that the top four artists in the field of dance music are: (1) Madona; (2) Beyonce; (3) Kristine W.; and (4) Rihanna. So clearly, the two things it takes to be a star in dance music are (a) a gay following and (b) no last name.