Interestingly, I had an email from Amazon the other day telling me that some of the CDs I have bought from them in the past (going back to 2005) are now available for me to download free as MP3 files. As it happened, of the three mentioned, I'd already converted two to MP3 files, but I was very happy to be able to download the third.
This is Amazon saying: Hey, you bought the CD, here, have the MP3 as well.
Maybe this really will happen with books and Kindles.
Tony, they're not doing this because they want to be generous--they (and the record companies) are doing this to market their MP3-purchase service in the hopes that you will make future purchases as MP3s, rather than CDs. After all, it's a lot more profitable for record companies to sell songs directly to consumers in electronic format that have to publish, package, warehouse and distribute CDs.
Book publishers, in general, are decades behind
record companies in terms of trying to push sales of e-books over print books, so I don't see "buy print books/get e-books" deals happening for a while unless certain publishers want to get out of the hardbound book industry entirely.