Apple is selling iPhones as fast as it can make them, but that may not be fast enough

Chinese queue up for iPhone 4S. Photo: iWorld

A pair of analyst reports Tuesday warn that Apple (AAPL) may be having trouble feeding the demand for iPhones in advance of the holiday selling season.

In a note entitled "Limited near-term upside for iPhone," Rodman & Renshaw's Ashok Kumar alerted clients that low yields on an unidentified "key component" is likely to constrain production of the iPhone 4S this quarter.

"Layering on the estimated 4 million iPhone 4S that were manufactured (but not shipped) in the September quarter, overall iPhone shipments in the December quarter could come in around 30 million units or below street estimates."

For the record, 30 million units is 3 million more than Kumar's own 27 million estimate, which he described in October as representing a "strong rebound."

Meanwhile, Susquehanna's Jeff Fidacaro cites equally vague "supply constraints" in a report that suggests a 2-3 million reduction in iPhone 4S builds for the quarter. Accordingly, he is reducing his iPhone 4S production estimates from 26-28 million to 23-25 million.

But "store checks suggest that demand remain solid," he writes, and when he throws in the iPhone 3GS and the iPhone 4, his total iPhone production forecast for the quarter is 29-34 million units.

Considering that Apple sold 16.24 million iPhones in the December quarter last year, that represents somewhere between 79% and 101% growth year over year.

Not too shabby. Which makes you wonder why these notes are being cast as warnings.