About a year ago I built a number of micro niche sites aimed specifically at generating adwords income for high ppc terms. They weren't especially pretty but they were a good exercise and more than paid for themselves. At the point I sold them (22 sites) they were generating about $190 a month in adsense revenue, all this from me buying 'keyword in domain' urls, having a relatively good eye for writing seo copy and b…
I also know some people with hundreds or thousands of these kind of sites and I can assure you they're not happy.
Building a business that depends on Google's algo to be profitable doesn't make any sense to me.
EDIT: When I say it doesn't make sense to me I'm talking about side-projects where the goal is passive income. If you're going at it full-swing and plan on pivoting as required then it can absolutely be a genuine business model.