I think the view-as section should be an un-ordered list with anchor tags, I don’t see it as a section. To me the section would be more where the div is because it is sectioning the content. So you have a list of buttons and a list of images in multiple columns, but that is just my take on it.
The only thing I would change is the section#view-as to a div, or even just a p. A section is used to group related content together, much like a div, but in a more semantic way. In this instance, there really is no grouping (looking at it single font-size chooser, and not a group of links). I also question if this is even needed today as most users are aware of their browsers abilities to zoom or increase font-size.
I disagree with Chris and Adman, and feel the sectioning of the images is acceptable. Of course, this is purely subjective.
I think based on his picture a unordered list would fit him better. I could be wrong but I see it as more of a list of options then as a paragraph. This is what I see him going for in regards to layout of the view-as and the images http://razorjack.net/quicksand/.
You are correct, I just did a bit more research with the W3C and basically if you can’t put a h1 or some type of header tag inside it, then it can’t be classified as a section, so a div should be used.