There are several examples I could use that should discourage even the most ardent music lover from this choice of music purchase. For me, however, the main issue is the way I use and consume music. The DRM tether of the Zune Pass means that you are only renting (or leasing) the music. As soon as you stop paying you stop playing!
My problem with buying music is not the fact that I cannot get lots of it, but that I cannot find lots of quality music that I enjoy. So for me the quantity is less important than quality. Usually when I find a great musician\artist I will enjoy it for several months at a time and then that music becomes part of my history ... the play list of my life if you will ;)
I am willing to admit that others may not have such an organic relationship to music and that treating music like chewing gum and moving to the next piece is a reasonable paradigm. Or indeed, gorging on as much music as possible regardless of the quality may seem like a fine way to dine. Or simply paying the $14.99 to test the music and then maybe purchase what you really like later ... isn't that rent to buy ... no thank you! I prefer my music à la carte not buffet!