As people said, it would be pointless not to include it, as physically speaking, it is possible to pick up two shields. Now, I hope they've balanced it properly so that it will be as useless as it would be in real life.
But hey, I think we should be able to dual wield bows. No, really. You just shouldn't be able to knock arrows if you do. You should also be able to dual wield torches, lanterns, lockpicks, forks, w/e.