Reggie recently said that be believed supply would be 'tight' but the DS would be available for most who wanted it. 'Tight' supply means it will be sold out at some stores. I believe online stores are a good indicator of it selling out at some locations, primarily because more people can reach any given online store in case the DS is sold in their area.

Nintendo has lots of DS units stockpiled for the holidays, so the shortages we're seeing may be supply chain issues or perhaps Nintendo needs to start shipping larger quantities. There should be enough in the warehouses considering the 2.5 million per month Nintendo has supposedly been producing.

I predicted in August that DS would ship 100 million by the end of December 2008.
http://www.vgchartz.com/forum/thread.php?id=5674

I'm surprised no one posted the "it prints money" pic again. The little handheld that could doesn't seem to be slowing down sales wise. Nintendo could stop making Wii's and still make a fortune off the DS alone.