Reasons why you should use external link Optimization:

Google Loves Links. Links are also the cornerstone of Google’s PageRank algorithm, links are so important to Google and it encourages people to create links (and conversely, discourage websites from not having any links out at all). The argument is that Google incents behavior that helps it deliver better results to its users. Nothing is more important than links between related websites to make this happen. So, we argue that if your website is overly frugal with outbound links, Google doesn’t like it as much as if you had at least a few strategic links that helps Google help its users. Our advice is don’t try to be an island – share some link love.

In addition to helping Google out by powering it’s PageRank algorithm, links are also a great “signal” for you to send to Google as to what topics your site is related to. As you might suspect, if you link out to an interesting article or two on a key topic of interest to your business, Google uses this as one more way to “figure out” what your site is about. So, in addition to whatever content you have on your page, the content you link out to is an important factor in training Google so it can establish context.

When you link out, especially in a consistent, opportunity-driven way, you build incentives for others to engage with your site. Don't underestimate the power of rewarding your community - it's built some of the most amazing brands on (and off) the web.