On the Kindles, the ads aren’t intrusive, and if you get an ad model and change your mind later, you can just pay the difference and get the ads removed. So it’s not much of a risk to just get the ads. This is the first time I have heard this... you would think they would market that ability more.
There are a couple of problems here: Amazon is allowing retailers to carry part of the line. Radio Shack has even fewer choices (mine didn't have the Touch at all). But worse, they have too many choices, and the retailers aren't able to (or are failing at) educate their employees on the devices. That couple I saw is going to be pissed if they take the device home and aren't able to remove the ads.
On the flip side, it encourages people to just buy from Amazon.com where you know what you're getting.