The IAB came out with 2006 First Six Months numbers on online advertising.  One interesting phenomenon that endures is the concentration of advertising revenue at the top.  The Pareto Principle does not apply to this case (in that it is even more concentrated than the 80/20 cliche.  The top 25 advertisers (NB: NOT the top 25%, but the top 25) pull in a whopping 84% of all online ad revenues.  Reminds one of the Turkish TV advertising figures…