After scrutinizing financial reports from Amazon, analyst Mark Mahaney estimates that Amazon has sold half a million Kindle digital readers–120,000 more than previous estimates.

The analyst also told Silicon Valley Insider he thinks that the company could have sold 750,000 units, but they sold-out the initial (undisclosed amount) of Kindles. As GalleyCat reported last week, the company is poised to reveal the next generation of the digital reader.

Here’s more eyebrow-raising speculation: “Mahaney now thinks Amazon’s all-in Kindle revenue could reach $1.4 billion in 2010, or an impressive 4% of Amazon’s revenue that year. This assumes that Amazon will sell 1 million Kindles in 2009 and 3.5 million in 2010; that Kindle owners buy one book per month, etc. It’s an admittedly rough estimate, but not necessarily an unbelievable one.” (Via TeleRead.)