As far as I know it was only during the free dining and I thought that was only done in 2006 not 2007. In Oct. there was no notice of the ability to do this.
It was also offered to some people during Thanksgiving week. However, you only got 1 CS for 1 TS. It was not made know to everyone. My cousin and his wife wanted to make ADR's the day they arrived (yes, I tried to tell her back in July when she first booked the trip that she needed to make ADR's but she told me she knew everything about the DDP) and couldn't get in any where. So they allowed them to trade. Made for a rather expensive CS meal as far as I'm concerned. In fact, they ordered a whole pizza at Pop's food court and had to use 2 TS.