As President-elect Barack Obama begins fleshing out his agenda, one promising sign is that he considers Internet infrastructure to be key, judging from both his stated goals and the caliber of people he's asking to advise him on policy.

I couldn't agree more. But before we jump into policy discussions, we should probably agree on some definitions. What, exactly, comprises an ISP? Is it a telco that also offers Internet connectivity? A wireless provider? What about a content provider?

I'm not being pedantic — the answers have far-reaching consequences for policy issues like universal broadband and net neutrality.

Take Amazon, whose Kindle device has transformed my life over the past eight months. For those who don't know, the Kindle's an e-book; a paperback-sized plastic device with a black-and-white display optimized for books and other written material. Its best feature, though, is the ability to deliver books instantaneously (or nearly so) through a free wireless link: Click, download, read.

For folks like me who are addicted to the written word, it's more compelling than caffeine. So Amazon provides the wireless connection, and doesn't charge users for it. (The actual network is Sprint's, but Amazon brands it as "Amazon WhisperNet.")

Here's where it gets interesting, though. This wireless link is actually an Internet connection, which is optimized to take users directly to the Amazon.com Web site. But like any "real" Internet connection, it also supports general-purpose browsing, e-mail and other applications.

In essence, Amazon is now an ISP — taking its place in my household alongside the wireless and cable providers that also deliver Internet connectivity. Yet Amazon's "Internet service" makes it extraordinarily easy to connect to Amazon.com — and extraordinarily cumbersome to get to, say, BarnesandNoble.com.

That is, Amazon's an ISP that unabashedly favors one content source (Amazon) over another (Barnes and Noble). And by doing so it violates the fundamental premise of net neutrality — which is not to prioritize content from source A over content from source B.

You may figure that it's no big deal, because nobody in their right mind would elect to subscribe to the Internet through Amazon. Maybe. But there's a rather compelling logic to "free" — and whether intentionally or not, Amazon has now created the first free coast-to-coast consumer ISP.