If you want to prohibit customers from specifying a shipping address that differs from their account registration address, then this recipe is for you. It removes the link to the Checkout Shipping Address page from your Shipping and Confirmation pages, and additionally, does not allow manual hacking in the URL.
Note
Chef's suggestion:
This is a decision you should make very carefully, considering all implications such as the fact that sending a gift directly to the recipient is no longer possible or that you cannot have customers order with their home address as the billing address have sent their items to their office. It is often an option for very expensive items though, where you need to make sure that all addresses match to protect yourself from fraud.