It is obvious that search engines will become less important as more and more traffic originates from social networking sites instead. I've seen numbers indicating that MySpace already has double the traffic of Google search.

Read the Online Spin blog article MySpace: Google's Frienemy? for some excellent insights on where this is heading.

I found the comments about Potential Rivals to Google Search quite interesting.

The reason this is pertinent to advertisers is that wherever the traffic goes that is where your potential buyers will be. For best results you'll want to diversify your traffic sources.