Earlier today we confirmed that Facebook is delivering updates to its Android app outside the confines of Google Play. The unconventional update method has alarmed some users and led others to question whether Facebook is somehow violating Android development rules. A source at Facebook has since informed The Verge that only a small subset of people are receiving the prompt to download build 141046 (and others).
In particular, only devices that permit applications to be "sideloaded" (installed from sources other than Play) are eligible to receive the update. Our source essentially equates the experiment to a beta test; it allows Facebook to trial new features with a small pool of users before rolling them out to the Android community at large. Furthermore, the update notification should only be displayed while connected to Wi-Fi — Facebook isn't trying to waste your mobile data — and you'll need to expressly grant permission for the installation to proceed.
We're still unclear on where Google stands in regards to Facebook's newfound strategy, and have once again reached out to the company for comment. We'll update you with anything we hear back.