E-tail kingpin Amazon.com (NASDAQ:AMZN) is working on a smartphone. This much we can already safely assume. The device may even approach the phablet category, with a 4.7-inch display, according to the most recent batch of rumors. Investors now have one more clue that Amazon is preparing to launch a Kindle Phone: the company has hired a former smartphone executive.

Charlie Kindel used to be a Microsoft (NASDAQ:MSFT) Windows Phone general manager, helping the software giant grow its smartphone developer ecosystem. Kindel spent over two decades at Microsoft and helped launch Windows Phone 7 before leaving the company in 2011 to launch a start-up.

Kindel has confirmed on his LinkedIn profile that he now works for the e-tailer and is "building a new team going after a total new area for Amazon." The list of totally new areas that Amazon could be exploring is rather small, especially ones where smartphone experience comes in handy.

This isn't the first Windows Phone exec that Amazon has grabbed from Microsoft. Another Windows Phone developer exec, Brandon Watson, made the switch last February, and Windows Phone director Robert Williams jumped ship last July to become director of Amazon's app store.

Don't forget that Jon Rubinstein, the former CEO of Palm, still sits on Amazon's board. While Palm's turnaround fell flat before being put out of its misery by Hewlett-Packard, Rubinstein is still a good resource to have, and he has experience launching smartphones. His years as a hardware exec at Apple reporting directly to Steve Jobs don't hurt, either.

At this point, Amazon has almost everything it needs to launch a smartphone. It already has a forked version of Google Android; it has a wide range of content services and apps; it has contract manufacturers already building tablets for it; it has existing relationships with wireless carriers that sell its LTE-equipped tablets; and it has plenty of smartphone talent.

The only thing Amazon doesn't have is a disruptive approach to pricing a Kindle Phone.

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