An interesting article regarding both the sales and virtual lines in the actual game come The Burning Crusade launch. A game as popular as World of Warcraft is bound to have queues at the stores to the extreme!
CareerLinked.com has the following to say:
We all know very well that a lot of stores do not guarantee results with pre-orders if there is too much demand for supply. So come that fateful Tuesday morning, there will be many disappointed gamers, what I would suggest is to start lining up now so that you will ensure that you get your copy and are able to experience the burning crusade as soon as it comes out.