I remain an unabashed iTunes junkie. But an alternative model — the "portable" music subscription — is growing on me. Now, with the addition of RealNetworks Rhapsody To Go service — and especially with the debut this month of Yahoo Music Unlimited — I imagine it'll grow on others, too.

I'm guessing that Apple will eventually introduce a subscription service of its own.

Why? Under a subscription or rent-a-tune model, you can listen to a boatload of music for a lot less loot than on a buy-only download site. And you can carry those tunes in your pocket, via compatible portable digital music players. Buying 2,000 songs on iTunes would cost nearly 2 grand.

Why rent when you can buy? Aside from the cost savings, you may want to listen to something on a whim. Maybe you're just curious about an emerging artist.