The recent Spotify update added some sweet-looking social features. I say they look impressive because Spotify has yet to release its service in the U.S. With at least four major music labels to negotiate with to get a critical mass of tracks, the woods are thorny indeed, but if they manage to clear that significant hurdle and roll out the following feature set, I'd be ready, at long last, to switch to a subscription service over the model of buying and owning my own music:

Sasha Frere-Jones wrote about the shift of online music to the cloud in a recent issue of The New Yorker. He mentions the usual players (Pandora, MOG, Spotify) and concludes that the age of the computer DJ is upon us.

Similarly, the anonymous programmers who write the algorithms that control the series of songs in these streaming services may end up having a huge effect on the way that people think of musical narrative—what follows what, and who sounds best with whom. Sometimes we will be the d.j.s, and sometimes the machines will be, and we may be surprised by which we prefer.

I think he's partially right. DJ HAL is doing a good job (you can throw Apple's Genius in with those other services), but I still suspect that what Spotify and what I'm sure will be an iTunes cloud-based subscription service will facilitate is the sharing of playlists and discovery among humans. I enjoy MP3 blogs, but I'd much rather follow the lead of musical tastemakers more directly through the same applications I use to listen to music rather than having to read their blogs, go find the music they reference, and then spin those into playlists in iTunes to transfer to my iPod.

Current bandwidths for WiFi and 3G are sufficient to stream music to my iPhone. I'm ready for a cloud-based music subscription service that adds a follower-based social layer (where you can find good tastemakers and choose to follow them even if they don't care to follow you). Such a service is dynamic and ideally improves and changes every time you visit it.

I'm ready for this same revolution to occur in books, too, and with Amazon's latest Kindle app, we're just starting to see the first pebbles of the avalanche skipping by our ankles.

Recently I read David Lipsky's Although Of Course You End Up Becoming Yourself: A Road Trip with David Foster Wallace on my iPad through the Amazon Kindle app. As I was reading, I noticed some passages had been underlined already. When I clicked on the underlined passage, a box would pop up noting "57 other readers have highlighted this passage".

Ah.

What was frustrating about the battle between Amazon and publishers over digital book pricing was that no one was talking about how to enhance the value of the digital book by capitalizing on what a digital, internet-connected book delivery service could provide, and that is a social reading experience. Publishers were demanding that Amazon charge higher prices for Kindle editions of books, but not once did I read anyone saying how they might justify that price hike by creating something more valuable for the reader.

In college, I hated buying used copies of textbooks, despite the significant price savings, because a book that was marked up and highlighted violated some aesthetic sensibility, especially if the previous owner had highlighted passages I didn't consider important.

But with the Kindle, you can enable highlights and notes to be turned on selectively. To pivot off of David Foster Wallace for a moment, recently the University of Texas acquired the David Foster Wallace archive. DFW was a voracious reader, and besides drafts of his writing the archive contains actual books from his personal collection.

There are also some two hundred books from Wallace’s own library. “Virtually all of the books are annotated, many are heavily annotated,