A Little Too Secretive
We understand that Google is engaged in a never-ending, and very high stakes, battle with the forces of web spam. That’s why they can never really reveal too much about what exactly it takes to grab those top SERPS. Doing so would invite certain chaos to their world.
At the same time, Google could definitely be more forthcoming when issuing warnings about bad links. This kind of information would actually help white hat SEO types more effectively navigate Google’s trickier policies.