Internet marketers used to optimize for the "first page" - in other words, being one of the top ten natural search results. While there was declining value with each search position, you could still derive significant traffic from lower positions. But as Google gets smarter and more sophisticated - the search page gets more and more crowded.... which significantly heightens the importance / impact of high rankings... and weakens the value of lower positions. Think about how Google's search results have gotten more crowded. Depending on the query and category, search results pages now include a mix of: photos, news clippings, product data, stock quotes, Twitter mentions, mp3 tracks, etc. SERPs have become more crowded, more colorful and - sometimes - distracting.
While the SERPs have changed dramatically and impacted traditional SEO, it also represents an opportunity for other creative traffic drivers. I have written about the SEO benefit of Facebook and Twitter, but there is significant, proven opportunity around photo, blogging, product and xml optimization.
Below are two screenshots of a newsworthy query (CJ Spiller - NFL Combine standout) and a product query (Tag Heuer). Notice how much of the SERP is not traditional "organic" results.