Earlier this month, Apple kicked Microsoft (NASDAQ:MSFT) while it was down, opting not to develop a version of iTunes optimized for Microsoft's ambitious new "Metro" interface. The Mac maker likely felt that it wouldn't be missing out on much, especially since the desktop version of iTunes could still be used in Windows 8, while Windows RT was the platform really getting left out in the cold.

Now Google's (NASDAQ:GOOGL) taking a shot at Microsoft by hindering the software giant's app availability, except this time we're talking about Windows Phone 8 as opposed to Windows 8. The search giant has been subtly trying to sabotage Windows Phone in various ways, including the refusal to make a native YouTube app for its rival's platform. As one of the most popular video content sources on the Internet, YouTube's official absence is a blow, even though there are unofficial and third-party apps available.

That's also in stark contrast to Google's stance with Apple, since it promptly released an official YouTube app for iOS shortly after Apple removed its own pre-installed version last year. It's a good thing for iOS users too, since Google's versions of its apps are actually better than the Apple-made ones anyway, including Google Maps.

Microsoft decided to take matters into its own hands and made its own unofficial version, tapping into available YouTube application programming interfaces, or APIs. Perhaps out of spite, Microsoft also went ahead and blocked all ads, which is YouTube's primary revenue source in the first place. Needless to say, Google was not impressed.

Big G has now sent a cease-and-desist letter to the Redmond giant, which The Verge got a hold of, requesting that Microsoft take down the app and disable existing installs. The ad revenue helps content owners monetize their content, so blocking ads hurts the entire YouTube ecosystem. Without a vibrant community of content creators posting videos, viewers and the world at large could be deprived of discovering the next Justin Bieber. That would be a tragedy.

In response, Microsoft has said it would be "more than happy" to include said ads if Google provides it with the necessary APIs. It seems that Google could theoretically continue blocking a Microsoft-made YouTube app by withholding these APIs, but Larry Page did call for the industry to stop being so negative toward each other, saying that's now how progress is made.

With Microsoft's YouTube app for Windows Phone, the ball is now in Google's court.