A disease is a "simple contagion". It can be caught by means of a single exposure to a single source, but multiple sources and exposures 'help'.
Contrariwise, many social phenomena are "complex contagions". To catch one requires exposure to multiple *sources*. Multiple exposures help, but multiple sources are the key.
So, I say to you that the act of gaming primarily
acts as a complex contagion, while the act of selling games is treated (as are almost all things in the market) as a simple contagion. This means that marketing and one-on-one action may produce buyers and collectors, but demonstrations, ongoing games, conventions, geek gatherings, and the like - those produce players.
I give you a reference here, from the American Journal of Sociology: ftp://hive.soc.cornell.edu/mwm14/webpage/WLT.pdf
Be aware that said reference starts easy, but also includes modeling of such stuff, and a lot of discussion on the kinds of ties over which things spread - short ties or long, strong or weak, and so on.
And I ask you this:If this is true, what else is true?