In reply to Chris Morrish:
Getting your feet measured for rock shoes is in fact for the assistant, so they can get a sense of the shape/volume of your foot in order to recommend a shoe. The size (length) of your foot does not affect in any way the size shoe you might end up with.
The author wrote about sizes varying from brand to brand and model to model, but I might add that they also vary batch to batch. I'm now on my fifth pair of Anasazi VCR's, and I've bought sizes 8 through 9.5, all of which are exactly the same size. A good reason not to buy online, even if you want to replace your current shoe.