Exclusive update by Joe Magyer

Amazon was back in the black in the fourth quarter of 2012. Operating income rose 55.7% on the back of wider gross margins and 22% higher sales. What fired up investors, though, was the climb in gross margin to 24.1% — Amazon's highest mark in a fourth quarter since 2001. The margin widened thanks to a higher mix of sales coming from third-party sellers and success from its budding advertising platform. Look for those trends to continue throughout 2013.

Not everything was rosy. Amazon's bottom line continues to look like a crime scene — the company posted a small GAAP loss in 2012 and its operating profit fell 21.5% for the full year. I was also nonplussed with first quarter sales growth guidance of 14% to 26%, the midpoint of which marks a slowdown and is below my expectations for Amazon's 2013 full year. And paid unit growth, which clocked in at 32% and was likely double the growth rate of U.S. e-commerce in the fourth quarter, was meaningfully lower than the third quarter's 39% year-over-year gain.

All told, though, this was a strong quarter for Amazon, which becomes more dominant by the quarter. The stock is richly valued at $283, though, and patient investors should consider waiting for a price below $260 to buy with some semblance of a margin of safety.

Joe Magyer owns shares of Amazon.com. The Motley Fool recommends Amazon.com. The Motley Fool owns shares of Amazon.com. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.