Oh, don't worry. I'm sure it didn't really cost them much in the way of sales since they still took the order and money at the time even when unable to deliver the product. The only thing it really cost them was a couple days worth of consumer confidence in their product (mobi DRM) though most people will probably misdirect their ire towards the bookseller instead. Actually, I'd like to see a few more outages. Perhaps that would get more books published in something besides just mobi.

(I honestly don't mind mobi but have a horrible dislike for the publishing of any single format exclusively and most books using a single DRM seem to use mobi. If you are going to DRM, use several so people have a blasted choice!)