Amazon's Kindle Worth $1 Billion

After early production runs sold out, speculation about just what kind of product Amazon's little white reader will be for the online retail giant (An iPod for books? A better Sony Reader? Something in between?) is now getting some closer attention.

Amazon (AMZN) has kept diligently mum on its real sales numbers, but Mark Mahaney, a Citigroup analyst, says they're looking much stronger than expected.

He pegs 2008 sales at around 380,000, double his earlier estimate. That translates to revenue above $1 billion by 2010, compared with his earlier estimate of $400 million to $750 million. It's also nearly 4 percent of Amazon's total sales—a number that puts the Kindle in the sort of territory that could make it a real growth driver if it can become one of this holiday season's "it" gadgets.

Amazon shares are up more than 10 percent today on the news.