Slack's (WORK) opportunity is almost unlimited as it could be positioned at the hub of the modern workspace, giving it access to numerous adjacent verticals. In addition, enterprise communication software is potentially an increasing return market where the leader becomes dominant and achieves high returns for an extremely long period of time (think Microsoft (MSFT), Oracle (ORCL), Intel (INTC), Google (GOOG) (GOOGL)). Outcomes in these types of market are generally path-dependent and difficult to predict due to the complex interaction of competitive forces.
Markets with increasing returns are often