Apple changed the online music industry with their "99 cents download and own" policy with the launch of the iTunes Music Store. Since then, iTunes has come to dominate the online music industry with up to %90 of the market share. (http://www.ipodhacks.com/article.php?sid=2191)
Apple of course wants to maintain this position. They are realizing that the market is now moving away from "buy-download-own" to "stream-listen-move on" model. I recently started using Lala, and Spotify, and my musically tastes are far larger and diverse when I don't have to worry about paying 99 cents for each song.
Apple purchased Lala to integrate it with the bare bones web iTunes they currently offer. (http://joshuadance.com/itunes-preview-apple-missed-the-boat) By offering a dual buy-or-stream model, they can keep their cash cow of 99 cent downloads and still stay on top of the rapidly expanding streaming services.
