Opening Statistics

What is the most popular chess opening used in competition? The Sicilian Defence would rank highly, as would the Ruy Lopez and the Queens Gambit. But then again, it would depend on where you look.
The Chessworld site keeps statistics on all the games played. To measure the popularity of openings they use a sample method (as opposed to a counting method), sampling from a set of games played when the site "matured" (ie after the first 2,000,000 games played).
Surprisingly the most popular opening is the Philidors Defence (1.e4 e5 2.Nf3 d6). Even I, who can usually construct an a priori justification for any result, struggle with a reason for this. Even assuming that most players on the site are casual players, I still cannot see why 2. ... d6 is instinctively better than 2. ... Nc6. In second place is 1.e4 e5 2.Nf3, and third is 1.e4 e5 2.Nf3 Nc6. I'm assuming there is no double counting of games, as otherwise the Kings Knight Opening would be a superset of the Philidors. Fourth place is less of a surprise at least in terms of casual players. It is Vant Kruijs Opening (1.e3). Other weird an wonderful openings included the KP: Patzer Opening (1.e4 e5 2.Qh5) in seventh place, and Damianos Defence (1.e4 e5 2.Nf3 f6?) in 15th.
As for the Sicilian, it checks in at 20th, just ahead of the Alekhines and the Caro Kan.