The folks at Google are getting a bit more serious about security for apps in the Google Play Store. Apparently, Google has banned app developers from performing updates unless they go directly through the Google Play Store. Here's Goggle's official statement on the matter,
What's interesting about this is actually how it came about. This new stricter policy was instigated by Facebook of all things. Apparently, the social network giant decided to update their pre-Facebook Home Facebook app, but did it directly through the app, bypassing Google's Play Store completely. Google was not happy about this, so they tightened up their policies.An app downloaded from Google Play may not modify, replace or update its own APK binary code using any method other than Google Play's update mechanism.