The story everywhere with respect to the Nexus One is shortage of supply due to lack of availability of the Samsung-sourced AMOLED screens used with the phone. 

Google would have been informed of the coming supply crunch weeks ahead of the wider market....who are largely left to watch the stock run out unless they have been watching the stories in the tech press about component shortages. Google appear to have tried to reserve their remaining stock for developers as the phone is the reference platform for development of Android v3.0. Those have now sold out, too. 

Looking in the rear-vision mirror, it looks like a case can be made for Google having decided to pull the plug on the online store at least in part because they knew they would soon face a supply crunch that would last months.....if it didn't last until the EOL for the phone itself.  

HTC are now building their own screen factory....but that won't provide any real relief for a year or more...and that would be *fast*. In the meantime, they have moved some phones to Super LCD (HTC Desire). 

Make sense? 

Maybe we'll see a Super LCD Nexus One?