You should bring it in-house as soon as it becomes critical for your business. Only startups that aren't profitable yet should bet their skin on so many hosted services as long as they allow them to grow faster (that's not a given, sometimes SaaS/PaaS are complicated to use and unstable).

When you are raking in profits, you'd better use some of them to secure your business and make it independent of such risks. Which is the point the blog post seems to be trying to make.