See this:
https://en.wikipedia.org/wiki/Network_effectThis is particularly useful when trying to find new events per se. For example, I see a friend marking himself "interested" for a particular event on Facebook. I do the same and reach him out on Messenger to ask him / her to go together.
I have to stick to Facebook because one way or the other, it gives me an avenue to socialize because people I know are there, use it regularly and are contributor to the network effect.