If we were starting from zero marketing, then some amount of marketing - say, a Sears catalog so I can tell what goods are actually being sold - is indisputably positive sum. It matches consumers with what they want to buy. But certainly there reaches a point where the competition becomes zero/negative-sum and you get the tragedy-of-the-commons you describe.
Much the same can be said of status competition - there's beneficial social skills "How to mediate a dispute" "how to accurately convey emotional information," "how to make small talk," but you continue to get selfish benefits after you pass well into zero/negative sum territory.
http://www.kalzumeus.com/2012/09/21/ramit-sethi-and-patrick-mckenzie-on-why-your-customers-would-be-happier-if-you-charged-more/
Surprising material to discover on Less Wrong, I know, but has some core insights about effectiveness and entrepreneurship and freelancing which I think people here will appreciate.
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