Facebook may start automatically streaming videos in your News Feed which could max out your monthly allowance and you could be charged extra for the overage on your data plan.
If you don’t have an unlimited data plan and your cell phone bill seems too high, you might want to try changing your ‘autoplay’ setting in Facebook.
Iphone users should tap ‘Settings’ -> ‘Facebook’ -> ‘Settings’ -‘Auto-play’ and then choose ‘Off’ or ‘WiFi only’.
On an Android device, start the Facebook app and then go to the account settings. Then click ‘App Settings’ and then choose either ‘Off’ or ‘Auto-play on WiFi’.