You must have missed the news behind that.people, why is future shop and best buy selling 4gb ipod nanos
http://www.futureshop.ca/catalog/subclass.asp?catid=23473&mfr=&logon=&langid=EN&sort=0&page=1&list=
andhttp://www.bestbuy.ca/catalog/proddetail.asp?sku_id=0926INGFS10111803&catid=24613&logon=&langid=EN
Apple was most likely going to have 4/8GB for the new Nano, then Microsoft threw a wrench into their plans with the announcement of the 16GB Flash Zune. Apple had to unload all those already built 4GB 4th Gen Nanos somehow.
It also explains why the 16GB models weren't available on launch but the 8GB models were. So far, no 4GB models in the US, most likely only outside the US due to exchange rates and the like.
Edit: B10 by NT1440