Markets, by their very existence, seem to create their own effects. Without markets, there are individual transactions between buyers and sellers. With markets, there are 'market prices' against which other prices are compared. There are speculators, futures, derivatives, traders, arbitragers, etc. Has there ever been a study of market effects, the kinds of phenomena that always seems to occur once a market is created?
This page was originally called "Market Effect." I moved it because the phenomenon of phenomena building up around markets can probably be usefully generalized to noticing that phenomena build up around all sorts of platforms. An obvious example is the field now known as "search engine optimization." This is a phenomenon that has developed because search engines (a platform) exist. People who sell search engine optimization services help web sites gain higher rankings on search engines. Search engines define a platform. This service exists only because that platform exists. But that service is a service to users of the platform. In that way it makes use of platforms the way market effect phenomena make use of markets.
Comment: It strikes me that this is a very large category of phenomena and relates to the proliferation of complexity that the emergence of what you call a platform makes possible through enlarging the adjacent possible space. I think this dilutes the concept of 'unintended effects' because it potentially includes just about everything that is emergent. (AM Grisogono)