Search engines must continue to deliver relevant, useful search results or risk losing market share.  As a result, the number of sponsor links per page will continue to be limited.  This will over time continue to drive up per-click costs as more competitors seek to acquire these terms.  The Answer - get good natural search results ranking. 

Advantages

• Credibility - Surfers believe the best companies are at the top
• No pay-per-click costs 
• Search engine providers share results so top listings may appear in multiple engines

Disadvantages