MMM has had 25 million views (per the latest post).
If these viewers altered their allocation of or saved an AVERAGE $50,000 during that time, it would be an economic move of $1.25 trillion dollars - definitely enough to move a market over six years. It would be an effect on par with corporate offshore accounts, tax cuts,
However, I bet that average is closer to $50 than $50k. Lookie-loos are a lot more common than cult converts. For every new millionaire who changed their consumerist life because of MMM there are 500 people who glanced, said "I couldn't do that!" and never returned.
Also, MMM gets the occasional media notice, but this blog isn't exactly a cultural phenomenon (yet). My friends are more interested in taking about their luxuries than their frugalities. Zero of the people I evangelize have ever heard of the cult.
It comes down to the old question "what if everyone became Mustachian"? I think the effect would be scarce investment opportunities, much lower GDP, and much higher quality of life. But that's not what we're seeing. The rise in economic inequality pretty much explains the gap between stock valuations and average family finances.