I think there's a balance to be set - in part because different people do have different standards of what is appropriate at mealtimes. Personally, I'm not a fan of the idea that kids should be well-behaved to the point of being cyborgs. This is largely due to the fact that I myself am not that well behaved and it would be terribly embarassing for the kids to be better behaved than I am

. Seriously, I think mealtimes should be fun and there's room for a certain degree of chaos.
That said, I think we can all agree that throwing food at other tables (or even at the same table) and breaking dishes is WAY over the line. Let us not, however, overreact to the point of terrifying the kids (or ourselves) into having to acheive sainthood in order to be allowed in the dining room. This is, after all, our vacation. A certain degree of silliness should be not just allowed, but mandatory

.
(Or put another way - as long as the "silliness" doesn't cross the line, I'm much more likely to join in than to be offended or object).