Found it...it is in the stickey labelled 2008 Dining Plan FAQ, you can click the link there and also look at the brochure
"Can I share meals on the Dining Plan?
Sharing is never permitted at buffet or prix fixe meals. Beyond that, this is actually two separate questions, addressed below...
Can I share meals with guests not on the Dining Plan?
No. The Dining Plan cannot be shared with guests who aren't registered as part of your hotel reservation.
Can I share meals with other guests on the Dining Plan staying on the same hotel reservation?
There is no clear answer to this. Consistently, guests seem to be allowed to share the meals ordered on the Dining Plan amongst the guests at their table, with the exception of fixed price meals, such as buffets or other all-you-can-eat options. However, this question was been asked directly to Disney via email, by a number of guests, and consistently, they have answered this question by saying specifically that, "sharing is not permitted." Despite several attempts to get clarification about that statement, no clarification appears to be forthcoming from Guest Communications, and nothing official has been released by Disney Dining to resolve the confusion."
Hope this helps. I know that some people have experienced where they could share and others not. I guess you could just ask when you get there, as long as you have no expectations you avoid any disappointment and frustration.