On Tuesday, Citi Investment Research analyst Mark Mahaney offered an educated guess: Amazon sold 500,000 Kindles last year, higher than his previous expectation of 380,000.
Mahaney bases his latest estimate in part on a regulatory filing from Sprint Nextel, a key player since the Kindle downloads books wirelessly using Sprint's network. The filing notes that 210,000 of "certain wholesale devices" were activated on Sprint's network during the July-September period by "wholesale partners prior to selling the device to the end customer."
Mahaney said in an interview with the AP that this is the first time Sprint has disclosed such a figure.
Amazon has not released sales figures for the Kindle — which debuted late in 2007 and retails for $359 — though it said last fall that it had sold out of the devices after an endorsement by Oprah Winfrey.
The company made another 45,000 book titles available for the Kindle in Q4 2008, bringing the total to 230,000.
The company is rumored to be releasing a new version soon.
In his note to clients, Mahaney estimated that revenue from the Kindle could rise to $1.2 billion by 2010 — which he thinks would be 4 percent of Amazon's revenue for that year.