This is really funny -- I actually went to purchase the book "Web Form Design" that is referenced at the top of this post. It linked to the publisher's site, and when I tried to buy it, they asked me to register with email, password, etc. So I went over to Amazon instead and bought it there!

(I realize that Amazon requires registration to purchase as well, but I already have an Amazon account of course -- but the publisher is not Amazon and if they had allowed anonymous purchase I would have gladly given them my money instead, in which case they probably would have made more profit on the sale).