The Kindle Touch and Invasive Advertising
jetheis.com
jetheis.com
It's nothing like either of these analogies. It shows ads on the kindle itself, which no-one else will see unless you show it to them, and you won't see when you're using it. If you don't want to then fine - pay the $40. I don't think the amazon sales page is misleading - it shows that your kindle will be displaying a full-page ad. Frankly the ones posted aren't very different from the example.
The Kindle is a device that almost never needs to be charged and has a pretty attractive form factor, so it's very natural to leave it laying around, just like you would a book. Because the ads are always displayed, it is naturally turned into a tiny billboard unless it's intentionally left face-down or hidden.
That said, you're right; I'm being a little picky and my problems could have been solved by just coughing up the money instead. It just doesn't seem like quite enough fair warning is given to the uninitiated (like me) as to just how heavy-handed the advertising is.