Having already unveiled an app marketplace, Amazon is already competitive with Google’s own Android Market. And though Amazon’s tablet would be based on Android, the combination of Amazon’s extended digital goods market only extends the competition between the two companies. Android may remain a dominant OS, but Amazon could steal some of Google’s thunder in Android’s overall ecosystem.

It’s clear that digital goods and services is an important aspect of the mobile industry, and that connected devices are becoming mere portals for our personal cloud, work applications and communication services. Amazon already has a digital music store, movie rentals and books. Google’s moving into the digital goods territory, having just launched movie rentals and books in the Android Market earlier this week. ArsTechnica argues that such a shift could diminish Google’s leverage points over hardware vendors, losing some control over the implementation of Android’s mobile software.

Mobile a focus for Google Q2 earnings

These are all concerns that may be raised during Google’s quarterly earnings call today, where mobile will be a focal point. Google shares are up since the Google+ launch, in anticipation of today’s call. But the company’s shares are down nearly 11% overall this year, from $604.35 on January 3rd to $538.26 at closing yesterday. Last year Google reported $1 billion in mobile revenues, though the expansion of iPhone retailers and the growing presence of third party Android markets could bite away at Google’s extended sales.