I want to underline that I'm arguing about double orders when it concerns clan-mates or confirmed allies!
So, how about a situation like this:
There are two clan-mates in a game (lets call them players: A & B) and they've discussed a plan for an upcoming turn.
It's about (lets say) 48 hours until the deadline when player A sends in orders that follow the plan.
Suddenly

, player A notices that player B stopped responding to e-mails and statrs worring that the plan might not work out if player B misses the deadline.
So, he cross-posts to both the GM and player B to ask if player be sent in his orders.
I ask: What's wrong with the GM telling player A if player B (his clan-mate) sent in his orders?
If the GM tells player A that player B didn't send in orders then A will send in a new set of orders (which I think most GM's wouldn't have a problem with, thanks BR for reminding this one).
And if the GM says B has sent in orders then nothing happens and everyone's happy.
Some might say that it's different from sending in two sets of orders but actually A could attach the new set of orders to the mail with the question and add:'If the answer is No then please use these new orders'. Also he could send the question with the new orders 5 minutes before the dealine...
trewqh