Despite theories that it would be consumers who were in short supply this holiday season, it seems that Apple is having trouble keeping up with demand.

After a highly successful limited-release of its iPod Touch earlier this year, the company is now running short of other models, notably the formerly-ubiquitous iPod Nano and iPod Shuffle at mass-retailers like Target and Best Buy.

Analysts estimate Apple will sell close to 21 million iPods in the December quarter, up 90% since the fall.

[via AppleInsider]