The general consensus seems to be that sites decline until they find a natural bottom, and then they begin to grow again, as the high-quality content (and the engine) draws natural growth.
I worry that the Oracle question's answers are too focused on debugging, rather than more general. I don't know how to address that, though, to get better answers. This is a case where "narrow" isn't helpful. I'm not sure the OP really said debugging in any case, but it is easy to see why the inference.
The actual problem arises in many situations, of course.