I've pretty much stayed away from this, because it does so often become farmer bashing, and while we don't plant GMOs, we do feed our animals 'conventional' corn, in very small proportions and we are farmers.
The whole expense argument is moot, as Shoe said. They change their labels almost as often as the fashions change, so why would it be difficult or expensive to just add GMO or non-GMO? I think it borders on the ridiculous.
On the other hand, how much government do you want? How many more laws can we stand?