Here's an anecdote for you: I am generally religious about reducing the length of funnels, because length kills conversion like nothing else. This lead me to once let the customers make two choices with one click: whether they wanted download or CD of the software, and whether they wanted to pay by Paypal or Google Checkout. The four combinations were laid out in a 2x2 table.
This proved immensely confusing for people, so much so that adding a shopping cart on top of two bare "download" or "CD" buttons caused sales to rise substantially, despite the fact that the shopping cart was a virtual riot of distraction and required minimally an extra click to get through.