It all seemed like such a good idea at the time, but that universe of paid links was a house of cards that was destined to fail. In hindsight, the link implosion that followed the Penguin update seemed inevitable given Google’s Saraman-like gaze.
Of course Google bears some of the blame for setting up a system that rewarded excessive linking that never really added much value to end-users. And, shutting down the whole show in vicious blow that left SEOs scrambling for answers was pretty heartless.
These days, successful link building seems to favor the conservative approach with an emphasis on authority sites and relevant content.