Madonna vs. David Bowie: Presentation Questions

Sorry for the delay, but here are the questions I offer up from my presentation:

-- Why do Madonna and Bowie go unpunished for their challenges to gender binaries?
-- Are they popular despite or because of these challenges?
-- What are the limiations of the appropriation of androgyny hand-in-hand with maintained popularity, and how do these limitations differ for the male and the female star?