I think the only consequence was when orders are marked as done, possibly people would not get the order update emails. I would think a lot of people probably don't get them anyway because of the general email problems. Certainly no orders have been lost on the system or anything major like that. We think this has only happened to 2 orders but it is difficult to really tell.
But anyway, that problem is hopefully fixed now. All order numbers now should start with "EX" and that will break the bitcoin preg_match filter.