I recently had to write javascript for a voting form so that a pair of tickboxes acts just like a radio button. Apparently the users would be able to understand it more easily that way. I imagine they did a breif user study and all teh users not used to the web wanted the form to look more like the paper equivalent.
So i've just spent a bunch of time coding stuff that i could do just by putting in a commonly used tags, but I have a horrible feeling that all the suers that have used the web before are going to get confused because teh checkboxes are acting just like radiobuttons, which may mean changing it back.