[Notes from the 2006 Digital Media Conference]   

The market has enjoyed 3 plus years of quarter over quarter growth in online advertising, which is big and it's getting even bigger... and becoming a huge part of our business at AOL.  Keeping up with the demand is a challenge. The 4 big players (Google, Yahoo, AOL and MSN) control 50% of the advertising dollars. Each of these players enjoy over a 100M visitors a month. The spending gap between the 4 major portals and the non-portals is huge (i.e. a billion compared to 400k)