Yeah, that's what I was trying to get at in a roundabout way by mentioning that the special offers didn't really me all that much until the Twilight binge began, but the lock screen really did. In designing placements for advertising in ad-supported software, I am a believer in looking for "Seducible Moments." See this article by Jared Spool on this topic:http://www.uie.com/articles/seducible_moments/
In the case of the Kindle, the seducible moment is probably not any time when I'm in the middle of reading a book. They happen when I'm at the end of a book, or on the home screen looking for the next thing to read. I'm WAY more likely to tap through and purchase something if I'm actively looking for something new to read right now. Also, Amazon knows a lot about me-- certainly enough that they shouldn't be showing Twilight ads to me. By shoving poorly-targeted ads into my face every time I turn the device on, they make it far less likely that I will have a favorable impression of ANY ad. At best, this kind of stuff causes ad blindness and halo frustration with the device as a complete product. The lock screen may eventually cause someone like me to fork over $20 to stop seeing Twilight ads, but it's hard to say whether that $20 is worth more or less than the revenue they might have received if the experience around the ads were better.
TL;DR: Kindle special offers as currently designed are at best a wasted opportunity, and at worst a nasty blemish on a wonderful product.