It's experience and observation. I started doing PPC and SEO back in 2006 and what I've seen over and over again is that Google is trying to black box as many o

It's experience and observation. I started doing PPC and SEO back in 2006 and what I've seen over and over again is that Google is trying to black box as many of the success factors as possible so that it is harder for people to game the system. For example, in SEO, Google continues to devalue on page optimization, and various methods of getting links because it break's Google's algorithms. So, they invent/demand the use of rel="nofollow" because otherwise they couldn't detect paid links. Google works very hard to tell people they should nofollow advertising links and whatnot under the guise that it's better for the internet or it's more ethical, but the reality is they need the nofollow "link condom" to keep their search engine from looking stupid and being easily gamed. In the PPC space, AdWords also does a lot of things to black box their system to make it harder to succeed. For example, they introduced "Quality Score" which is a metric they can use to rank ads, which seems nice. But originally they had a simple CPC * CTR bidding system which was simpler and easier to game. More importantly, it made it hard for Google to maximize profits because if someone had a really high CTR ad, it would effectively lower Google's ad rates. In reality, QS adds a layer of indirection where Google can tweak various quality metrics to raise their advertising rates in subtle ways that people won't complain about because instead of saying that they are raising rates, they can just lower a quality score and you have to bid more if you want traffic for that keyword. After they rolled out the quality score system initially, I believe then CEO Eric Schmidt was quoted as saying something along the lines that they are able to show fewer ads and charge more while creating a better user experience. That's a nice way of saying they're raising their advertising rates. In short, Google is always struggling to balance between making more money and maintain a certain user experience. To achieve that goal, they create these black box systems that are harder to influence individually. That allows them to periodically raise their rates and "improve quality". I'm not sure I would do anything dramatically different if I were Google, but their black boxes and social engineering efforts should not be underestimated.