Too many people started building backlinks just for SEO purposes. Not only has Google caught on but you also quickly loose credibility. The only true value of link building is to build a real network. This in turn will benefit you with SEO and link juice.
Develop Real Networks, Not Just Link Networks
Links are the arteries of the web. Traffic flows via links, be they PPC, hyperlinks, or Facebook friend requests.
Of course, SEO's worked out some time ago that hyperlinks have another value. Google uses links to "keep score". To paraphrase, if you have a lot of "good quality" links pointing to your page, Google gives you a high score, and rewards you with a high ranking.
This way of thinking can cause problems.
If our link building strategies only relate to ranking, and not link traffic, then we're vulnerable to changes in the way Google keeps score. If, however, we look at link building in terms of traffic, arriving via those links, then we're less vulnerable to Google's whims. If, for whatever reason, we are no longer ranked well, we'd still have traffic flows via the links.
This is not to say link building for the purposes of ranking is redundant. Google's not that clever. Yet. However, if we're overly focused on ranking, which is one form of traffic acquisition, and not spreading our traffic acquisition methods, then it leaves us vulnerable to Gogole's ranking methodology, over which we have no control.