Yes, Facebook has just overtaken Google Search in traffic. What does that amount to? Nothing significant, if a study of the revenue per unique visitor (total revenues divided by the number of unique visitors) was calculated.
Here are the numbers according to data collected by ComScore:
Google : $18.44
AOL : $12
Yahoo : $6
Microsoft : $4.42
Facebook : $3.09
Twitter : $0.62
Silicon Alley Insider puts the study in context:
To estimate these numbers, we took the full year revenue for 2009 for each of the companies below (owned-and-operated sites only) and divided them by their average monthly worldwide uniques. The bottom line: Search gets the most per visitor, then display, and then social.
Did you notice that Twitter gets close to nothing for its traffic?