Facebook used to throttle devices once a week to make devs dogfood bandwidth in developing nations--I think it's much more top of mind there than we give them credit for.
As a developer, I only use my app on 64kbps speeds.
At those speeds, the only webpages still working are a few blogs and HN, and the only apps still working are whatsapp, some special irc apps optimized for that such as quasseldroid or irccloud, some reddit readers, and, if you have a lot of time, imgur.
Most of these also have app sizes in the kilobytes to single digit megabytes, making downloading possible within of a few minutes on 64kbps (essentially dialup).
Those speeds are basically guaranteed anywhere in the solar system, and if your app works with that, it basically works everywhere.
I don't think Facebook forces them to download new versions that day. Because responsiveness is clearly more top of mind with them than download time/cost.
