Do you own your favorite movie or do you rent it every month out of the year?
I have netflix. Ever since renting movies through them, I buy them less. Because if I want to watch it, I can just have it sent to me when I feel like it.
Renting movies is MASSIVE business. Music will be the same way, whether you like it or not.
I never see how options to consumers is a bad thing.
Oh, and you don't lose all your music. You only lose access to content you didn't buy, much like renting movies from netflix or games from Gamefly.