All advertising today is arbitrage by definition -leveraging a discrepancy between the value of those eyeballs and the cost to attract them. All arbitrage will eventually be corrected by the market.

This is why there is such a strong push to content marketing, which is essentially the brands becoming media companies.

This is also why native ad units (not just advertorials but any ad unit that Is the atomic consumption unit of the site like news feed ads, AdWords ads, etc...) Work much better than display, because they are value add and are essentially the flip side of content marketing.

I think the future, sustainable strategies will be user experiences that naturally progress into buying. (I.e. a content site selling premium content or hosting a conference or a Saas product using a freemium model.)

Maybe ads are called ads because they should be adding value.