It's a hot topic. I know what you are thinking? Will my roomie ever clean the bathroom? This is especially a problem for males, students, and young persons.
Well, this is how I got my roomie to polish it all up without threats of violence or the supreme court getting involved.
One day I tacked an envelope to the wall. On it I wrote "Great American Bathroom Sweepstakes", and wrote in the rules. Every week, each roomie would put a dollar in the envelope and initial it. The money was free for the taking to whoever broke down first and cleaned the lou.
I hardly saw my roomie, but he faithfully added a dollar to the envelope each week. On the 4th week I came back from class to a sparkling bathroom. My roomie smiled and said "I really needed the money".