Focus on the Long-term

One of my favorite papers of all time is "Focus on the Long-Term: It's better for Users and Business" from Google Research. This paper found that Google makes more money in the long-term -- when carefully and properly measured -- by reducing advertising. Because of this work, they reduced advertising on mobile devices by 50%.

tl;dr: When you increase ads, short-term revenue goes up, but you're diving deeper into ad inventory and the average ad quality drops. Over time, this causes people to look at ads less, click on ads less, and reduces retention. If you measure using long experiments that capture those effects, you find that showing fewer ads makes less money in the short-term but more money in the long-term.

Because most A/B tests don't measure long-term effects properly and this is hard for most organizations to measure correctly, the broader implication is that most websites show too many ads to maximize long-term profits.