With index funds so big, who determines prices? An index fund tied to the S&P 500 just buys stocks in the proportion that they're in the S&P 500. The price of the stock plays no role in that decision. At some point, this has to create problems, but so far it hasn't. It does mean the active traders, who are basically moving the same money around all day, have an outsized influence on prices. Index funds are so success…
I'm not 100% sure I understand the argument or have presented it correctly. It's reassuring.
The other takeaway here is that if you have a theory that ETFs are going to become increasingly popular, you could "test" that theory by investing directly in companies with run ETFs.
For example you could buy some NYSE:STT or NYST:BLK and that might help you invest in "people pay a premium for the liquidity and other benefits of ETFs". Of course, you'd want to believe that that theory will outperform the S&P 500 :)