Really we need to ask about the frequency and intensity of genocides before Facebook or without facebook availability. E.g. if we could find proxy countries, like ethiopia but with more, less, or no Facebook use, we could compare genocides in each country.

Maybe take "communication" instead of just Facebook so we could go further back in history if there is a good way to objectively measure how much communication is happening.

Hard task for sure, but I'd be interested in reading about it if anyone has done so.