It was a simple question, and one that underscored the major topic of the panel. Of course links now play a larger role in getting a new domain to produce search engine traffic, and also to establish trust, relevancy, and themes with the search engines.  Great links ultimately represent what other people say about you (off-page), and more often than not trump what you say about yourself (on-page).

The importance of on-page optimization, internal linking, maintenance, content, and internal site control

What is usually lost in this question is that search presence doesn't end at links alone, and that good on-page optimization is needed to round out the picture to fully take advantage of the opportunities that strong link equity and off-page factors bring.

At the end of the day, if you have off-page credibility, then the engines will pay closer attention to "what you say about yourself."

For many established Web sites--particularly for Fortune 500 company sites--deeper introspection about internal optimization strategies is often more pressing than the issue of link building.  

 External search factors - The Fortune 500

Over the years, I have found that most Fortune 500-level clients require different search approaches than small-to-medium sized businesses, or other companies that are building new sites, mainly because these sites are already well established in terms of theme, age, authority, freshness and trust.  From an optimization perspective, these sites are like a garden ready to grow, and search performance is directly proportional to how well the seeds are planted and tended. 

With link development and the age of the domain being major external factors in how search engines view websites, consider these statistics for the 2006 Fortune Top 10 (Google PageRank is also provided to show overall perception of off-page factors):

1. ExxonMobil.com: 83,810 links; online since November 25, 1998, PR7

2. WalMart.com: 2,222,709 links; online since February 25, 1995, PR8

3. GM.com: 243,091 links; online since January 16, 1992, PR9

4. Chevron.com: 71,468 links; online since April 13, 1990, PR8

5. Ford.com: 294,752 links; online since September 1, 1988, PR8

6. ConocoPhillips.com: 38,249 links; online since January 13, 2001, PR8

7. GE.com: 312,236 links; online since August 5, 1986, PR8

8. Citigroup.com: 132,977 links; online since April 6, 1998, PR8

9. AIG.com: 82,227 links; online since October 25, 1995, PR7

10. IBM.com: 4,441,167 links; online since March 19, 1986, PR9

Link source:Yahoo Site Explorer

These sites already have major search engine credibility when it comes to off-page factors, thus making internal strategy even more critical for these companies. This does not mean that link building efforts should be abandoned, only that internal factors should be treated with higher importance in the grand scope of search marketing efforts and that resources should be balanced accordingly.  For sites such as the ones listed above, refocusing on internal site management can also help identify future areas to target external link development, especially in thematic areas where the site may not be performing as well. 

Major sites, take note: These are some additional reasons why internal site optimization and maintenance is alive and kicking for established corporations, major destination and authority sites, and other highly-popular destinations:

You've got links:  Most Fortune 500 sites have already accrued anywhere from thousands to millions of links.  Proportionally speaking, search efforts and resources may be best put forth into maintenance and development of the legacy site for search benefits. 

Your major theme has been long established with the engines:  As noted above, major site themes for legacy sites are already largely established by the major engines.  So a major airline should expect to have an easier time using internal optimization strategies to rank for the term "flights to Dallas."

You're already a link magnet: Sites with Fortune 500 link momentum tend to pick up links on their own, either from news sources, blogs or efforts from their own PR department.  When your CEO speaks, people link. 

Your foundation is set: Fortune 500 sites are not designed on new domains, they are most often re-designed on trusted legacy domains containing volumes of existing authority links.  Treat your legacy links with great care, because your search presence is more dependent on your own site handling, rather than the way engines handle your site.  (See my article  "Natural Born Search Killers.")

Negotiating internal changes is key: The internal dynamics of Fortune 500 sites and development teams can change more often than the search engines do.  This changes the SEO game, in the sense that success is determined to a certain degree by how well internal sites' changes are managed and negotiated.