The Play Store has undoubtedly matured in the past few years, since graduating from the Android market and it now offers all manner of content. At the heart of it all though, are the apps, and nowadays developers are constantly tweaking, fixing bugs, revamping features and more. Which means they need to get these updates out there in a timely, seamless manner to reach all of those that have that particular app installed. For the most part, it works really well, you're notified when there's an app to update and you can even set them up to update automatically. Facebook, of course it had to be Facebook, decided to do things differently, and went rogue.
Recently, the Facebook app for Android added the feature to automatically download and then install the latest version of the app outside of the Play Store. Obviously, this has irked Google - as it should - and so with the latest update to the Play Store (v 4.0.27) there has been a change in policy that now states the following:
An app downloaded from Google Play may not modify, replace or update its own APK binary code using any other method than Google Play's update mechanism.
You hear that, Zuckerburg? While it's probably not aimed directly at Facebook, it certainly seems Facebook's decision to update on its own was high-profile enough for Google to make changes to the policy that now clearly forbids such a thing. Frankly, it's a good change.
Android might not be as "fragmented" as detractors like to make out but, things like one, unified app store keep things together and if apps went off and updated on their own then things would get pretty messy, pretty quickly. For instance, there are a myriad of security concerns involved with something like that, an unscrupulous app developer could install a modified APK just filled with nasties and the user would be none the wiser and Google have little power over it.
There's nothing wrong with the way that Google updates apps through the Play Store either, sure the delta APK initiative hasn't taken off but, it's simple and easily policed at the same time.