SEO & Marketing

• #5 - Linking Out Sends Trackable Traffic
  If I link to a great site for finding local classes & teachers or this one for automotive advice or this resource for all things TV and they get even a smattering of visits, it's very likely that the website tracking folks will notice the link, visit SEOmoz and investigate. Maybe they need SEO services or would be interested in some of our spiffy tools. Perhaps they'll enjoy this post and link to it in the future. What I'm getting at is that we (all of us, not just SEOmoz) have the potential to attract important, relevant, valuable eyeballs when we link.
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• #4 - It Makes Your Site a More Valuable, Scalable Resource
  No matter how great a website you build, you can never be all things to all people, nor contain all the relevant information & value a user might be seeking on your given topic. As such, it makes great sense to leverage the power of the web - the power of links - to create an easy, scalable path to making your site's experience better and more rewarding for those who visit. If you find great links via Techmeme or Hacker News or SearchEngineLand, you're going to mentally reward those brands with positive appreciation and memories. Use that same power on your own site and you, too, can become a reference resource in your niche.
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• #3 - Search Engines Likely Reward the Behavior Algorithmically
  Our Linkscape team has spent a lot of time looking into spam analysis and stumbled upon some pretty cool theories and applications. One in particular that stands out is the so-called reverse or "anti-trustrank" that looks at who you link to as a signal of quality vs. spamminess. While it certainly pays to consider the links you've earned, looking at the links you send can be an equally usable and useful signal of quality - low quality sites tend to link to a far greater share of junk, while great sites typically link to other great sites. These webs of trust & value can be algorithmically mined by engines to produce better search results. Take advantage by linking to resources your users (and the engines) will love. (BTW - just internally speaking, we really like using Linkscape's Domain-Level mozTrust metric for stuff like this.)
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• #2 - Linking Out Incentivizes Links In
  With a few notable exceptions (Wikipedia & YouTube, I'm looking in your direction), websites that earn links tend to do a good job of linking out themselves. When you link out, it creates a signal to other websites and content creators that you're a willing participant in the web's natural linking environment and not a closed-off community or purely self-referential, pompous know-it-all.
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• #1 - Linking Out Encourages Positive Participation & Contribution
  There are a lot of very smart, very dedicated, talented people on the web that can either contribute to making your efforts more successful or inhibit your growth. When you link out, especially in a consistent, opportunity-driven way, you build incentives for the Linkerati (bloggers, social media sophisticates, online journalists, website builders & forum participants) to engage with your site. Granted, when you're small and just starting out, the incentive is small, but I've seen, via first-hand experience, the value it brings. Don't underestimate the power of rewarding your community - it's built some of the most amazing brands on (and off) the web.

A big thank you to Rand Fishkin
Read the post, How Effective are Outbound Links, and comments for more interesting discussion about the potential SEO-specific benefits of linking out.