I was (digitally) leafing through the latest Lehman Brothers Internet Data Book for August this morning, and came across these forecasts for total U.S. Internet online ad spending and online video ad spending.
Video ads are the hottest area of growth. Analyst Doug Anmuth thinks that online video ad spending will reach $1.1 billion this year (up 63 percent), and more than double to $2.4 billion over the next two years.

He also thinks that total advertising spending in the U.S. will go from $26.1 billion this year to $45.5 billion in 2012 (consequently increasing from 8.8 percent of total advertising spending to 13.7 percent).

Here are some tables with his estimates:

Also, to give some perspective on where online advertising is compared to TV advertising, he offers this comparison chart of the first decade of broadcast TV advertising VS. cable TV advertising Vs. Internet Advertising. The 30 percent growth rate for Internet advertising is double the rate of where cable advertising was at the same point in its history, and triple the rate of broadcast TV advertising. There, don’t you feel better already?