If, say, social media world, nobody is unknown, because at least then people would ever play and spend time with it. The social world allows you to select multiple categories, use.
If to talk about social world still do not know, because at least then everyone must have played and spent their time with it. Social world, there are many types to choose from.
If talking about social world online, no one does not know at least that everyone had to play and time with it. The online community is for you to choose several types.