It's a tricky situation. I might be getting ripped off at 99 cents a song, but at least I can legally keep my songs forever. There are ways around the DRM, but with Yahoo's service once you stop paying your $5 you've just lost all those songs.
If I invest $60 in iTunes track (Same as a year of Yahoo! service) than I've got at least 60 songs that are legally mine for life. If iTunes raises the price of tracks, I can stop and keep what I've got.
If Yahoo raises their monthly subscription cost, you have either got to start paying them more to continue to legally use your tracks, or loose all your music.