Dana Baran over at WebGuild blog has a great short article summarizing Microsoft’s case against a Google takeover of Doubleclick.   The chart (from the MS legal team?) has what appears to be an excellent summary of the total online advertising spend.  I assume this is for 2006 but not sure.   It shows approximately a 20 billion total ad spend with Google scooping up 30% followed by Doubleclick at 22%, Yahoo at 19%, Microsoft at 17%, and all the rest at 12%. 

Microsoft’s point seems to be that Google and Doubleclick should not merge because, as the two leading recipients of online advertising revenue, this would create a player with more than half the market and thus too much power over the marketplace and advertisers.