While dual wielding shields doesn't really sound like a very practical choice, I see absolutely no reason why we shouldn't be able to do it. I might try it at some point just for fun, but I doubt I'll do it as a regular option, shields will probably be best used in one hand while wielding a one handed weapon or spell in the other.
A purely defensive (time buying) stance, or a controlled retreat, or high resistance as you run the gauntlet somewhere, or... dual equipped magic shields that do damage to attackers. :shrug:
I agree... It would be pretty cheap if you can equip two shields, position yourself out of melee range, and shout your opponents to death.