Investors long accustomed to thinking of Google as the leader in online search and Amazon.com as the king of commerce may be surprised to learn of the growing rivalry–some might say hostility— between the two companies. Only last week The Wall Street Journal suggested that Google may be speaking with brick and mortar retailers about a one day shipping service that would up the ante on Amazon’s two day free shipping service, which it provides to its most elite customers. If the report is true, one would surmise that Google could only have had the intent of taking Amazon off guard, in advance of the critical holiday shopping season.

Given the vast no man’s land which defines the border between ecommerce and online search, one may ask where the seeds of this now bitter rivalry were sewn.

We would speculate that it began with Google’s bold online book initiative, in which it sought to scan the world’s out of copyright book collection ensconced in the bowels of the nation’s great universities, including the University of Michigan. With the intent of making hard to find texts available online for the first time, Google’s ostensibly altruistic effort, lauded by researchers, became the object of scorn among the world’s publishers and authors who resented Google’s efforts to corner the market on out-of-print, and out-of-copyright books, without due consideration to paying author royalties.

Amazon.com, no doubt looking to fend off a challenge to its position as the world’s dominant online book reseller—which, by the way includes used, out of print, and out of copyright books—saw it as an obvious threat to its franchise. Thus, it joined forces with Microsoft and others to fend off the Google challenge.

To make a long story short, a period of détente began to emerge between Google and Amazon.com when Google sensibly abandoned or at least temporarily suspended its book initiative. Amazon.com, in keeping with its sophisticated yet sphinx-like approach to ecommerce (see Amazon.com: ecommerce Sphinx), began to sell Google’s internet PC on its website. Amazon.com, in a gesture of rapprochement, selected Android as the operating system for its new tablet, the Kindle Fire.

Dissatisfied with the pace at which the rest of the world was adopting Android, Google suddenly, in our opinion, lost patience with the pack of Android licensees, and purchased, out of left field, Motorola’s Mobility unit, whose Xoom tablet places it in direct competition with not only Apple, but Amazon.com.

Thus, the ante has been upped in the tablet wars, with Amazon.com’s Kindle Fire an increasingly sure bet to become the number two tablet in the next 12-18 months. This probability may have been realized only recently by the Googlers, and serves to explain—or at least better understand—its controversial decision to acquire Motorola’s phone and tablet group.