Ok, so all the books and magazines tell you that you should register in at least two places.  I understand the rational - of course I wanted my guests to feel like they could purchase something within their budget.  (Actually, to be honest, I was happy to recieve gifts, but I would have preferred to send a note out saying it certainly wasn't an obligation.)
That being said, if you have certain things that you really want to recieve, then don't register in two places.  However, if you want a specific set of dishes, register each plate or bowl or whatever separately.  Yes, you may not get the entire set, but there are registry completion options post-wedding.  But you'll more than likely get what you'd like rather than having that registry site that you only opened because you felt obligated to have two.  (Trust me when I say that, per Murphy's Law, they will all buy you stuff off your half-hearted registry.)