I've got my serial number and I just had Amazon send it all of the roughly 200 ebooks I bought. Hey, no removable card right, everything is backed up on their servers and if I'd tried to copy the content from my other kindle the DRM would probably have shut me down. So the way I figured it, ship 'em all, why take chances on the DRM?
Some of them are 20MB to 40MB each (I've bought a few worthy tomes.)
The question I have is I wasn't able to set the destination for my pre-orders: Frommer's and the Eating well book. It'll be interesting to see where they wind up.