The news broke on Twitter late last night -- Amazon had pulled first all Macmillan ebooks, and later all Macmillan books (incl Tor) from their site. You could buy them via 2nd party sellers, but not directly from Amazon. The assumption is being made that this related directly to Macmillan's agreement regarding the iPad.
This all happened at the start of the weekend -- interestingly, the same time as Amazon's "glitch" that deleted all links to gay-themed books a while back -- so there hasn't been any official word from anyone. But I'm inclined to be of the "fool me once" philosophy when it comes to Amazon's weekend glitches, myself.
Something to definitely keep an eye on, especially if you a) have books out from one of the publishers involved with Apple, or b) you're a reader who dislikes the idea of one retailer dictating what will/won't be made available to you-the-consumer.
This isn't about pricing; it's about control. Amazon isn't doing this to keep prices down for the readers, it's fighting to the death for its majority market share. Once they have it -- they will have readers over the barrel even more than before.
NYT linkage: http://bits.blogs.nytimes.com/2010/01/2
BoingBoing coverage: http://www.boingboing.net/2010/01/29/am
EtA: There's now a squib on the front page of BookView Cafe with appropriate links and graphics that says: Book View Cafe Ebooks: All our titles available 24/7/365...unlike some places.. I <3 my publishing co-op, I really do.