One of the main purposes of any search engine marketing effort to boost the rank of a website in the search engine rankings, and thus, achieve more search engine exposure.  That exposure, in turn, should drive more traffic to your site.  With the right content, and compelling services, more traffic can lead to higher conversion rates, more sales, and a more successful company.

But as Pandia Search Engine News points out in "Search engine marketing spillovers", the focus on higher search engine rank shouldn't be the ultimate goal of SEO.

There are a lot of added benefits to a good search rank that, in time, can be far more beneficial than the initial search engine rank boost.  They've dubbed these benefits "spillover" but you can call them whatever you want.  Think of it as a snowball effect of sorts:

• An "expert" site links to you, which gives you a little boost in the search engine
• Readers of that expert site blog about and link to your site
• Some of those readers (and their readers) bookmark your site in social bookmarking services, leading more people to your site
• People start signing up for your RSS feed
• A post gets submitted to Digg
• A journalist with a major publications sees your post on Digg
• A newspaper article by that journalist leads even more people to your site

The Pandia example goes on.  And so could the snowball of exposure.  In the long run, the bookmarking, Digging, feed subscriptions, and general coverage can do much more for your site than the short term goal of a boost in page rank.  But it's not an instant chain of events.  Building a quality site with quality linkage and good exposure takes time.  The point of the Pandia article is simply to set your sights a little further than simply a ranking boost.

Think of the benefits of a snowball or spillover effect like the one mentioned above.  Ultimately, your content - not your keywords and links - will make something like that happen.  So while it's a good idea to put some of those SEO practices into affect, you'll never get the added benefits or spillovers without good content.

SEO is important.  Good content is critical.