I would like to +1 this thread: http://www.magentocommerce.com/boards%20/viewthread/40273/#t428770
This quote from 'egyember' sums it up
To be honest the reorder button would be very useful on Guest orders as we could just copy all the customer details (name, email, address) onto the new order. Currently, you have to manually copy over the details from the previous order.
Question: How can we add a re-order button on order-level, that does one thing only: copy all the order details to a new order.
(would be a simple and I think great extension)