U.S. online advertising totalled more than US$12 billion in 2005, reached nearly $16 billion in 2006, and exceeded $18 billion in 2007, according to WR Hambrecht + Co.

In 2005, search and display accounted for two-thirds of the total ad spending, with $5.13 billion and $4.25 billion, respectively. E-mail classified was ranked as the third, with more $2 billion. Referrals and online video made up very little.

In 2007, search still owned the lion's share, and grew to $8.81 billion. Display also gained more than $1 billion to $5.66 billion. Referrals were almost flat, still representing a niche, while e-mail classified dropped to less than $2 billion.

Online video, however, jumped from merely niche in 2005 to $1.8 billion in 2007, according to WR Hambrecht + Co.