The sooner that everyone realises that, the better. It's a poor business plan that means a third party can, on a whim, destroy your revenue stream.
That's just the thing. Only online it is considered a legitimate business model to rely on one of your competitors to publicize your business. We here should all know better.
That said, a LOT of people in business don't know much about Google. I've talked to successful site owners who have never heard that their sites could disappear overnight from Google someday. Fortunately, the ones I've met only get 30-40% of their traffic from Google. But the natural assumption is that the SERPs are more stable than they are, and most people think this forum sounds like a bunch of conspiracy theorists being ridiculous.
When they started they worked on an algorithm that they let decide what a strong site was. So the serps were the result of the algorithm, now it seems the algorithm is led by the serps. The goal seems to be an algorithm that automates what they would do if they were left to hand edit the serps.
This is a great point, and it's reinforced by the fact that the webmaster guidelines and Matt Cutts' advice keeps getting more specific. In another thread, I described how in a video Cutts said you shouldn't create a site that does a lot of ranting because that's just an SEO tactic. This left my jaw on the floor, because no one can tell a linkbait rant from a genuine rant. This is stupider than the idea that Google can always tell a paid link from an organic one with perfect accuracy.
They started with helpful advice about coding. Then they invented codes they wanted us to use, which was annoying (really? we have to put nofollow on links just for Google's half-ass algorithm?), but whatever. But now I feel like Google is pushing hard to make us rewrite the web in the image they have of it. Their point of view, their idea of polite expression, their idea of what's an important topic. I have a bad feeling they see themselves as a benevolent dictator.