Don't Tell Guests Where You're Registered in Your Invitation
Once you have registered, give the information to immediate family and the wedding party, and let them spread the word. If you are asked where you have registered, it is fine for you to tell, but it is not proper to include registry information in a wedding invitation. Registry information can be included on a wedding website, as long as the actual name of the store is not included on the same layer; organize your website so that guests must click down one level to find the details.
Thank you, Martha Stewart (er, your staff) for coming out and saying what I have always thought; may many brides-to-be read your website and follow your advice.