Border-radius proposal

Greetings, all!

The moderator of css-d suggested this might be a more appropriate
forum for this proposal.  I was wondering if anyone had considered
allowing negative arguments to the border-radius property to create a
sort of scooped-out rounded corner -- like you might see on an
old-fashioned movie ticket or a decorative border.  It seems like a
fairly logical, and useful extension of the existing behavior.  What
do you think?

Sean