While there are certainly economies of scale that may allow others to do better anyone can engage in some sort of advertising, guerilla marketing is definetly a

While there are certainly economies of scale that may allow others to do better anyone can engage in some sort of advertising, guerilla marketing is definetly a decentralized advertising tactic. If monopoly is defined solely in terms of dominance it is ironically possible for there to be a decentralized monopoly as technically anyone can enter by any means but there is one big fish in the pond. I dislike that definition of monopoly personally because a monopoly with no concrete barriers to entry feels like an absurd abuse of the term.