Dig this article by Nate Silver as part of the free BP: it’s called Lies, Damned Lies — Shrinking the Ballpark and concerns the fewer number of seats being built in most of the planned ballparks. With the opening of the new Yankee Stadium (which has 6,000 fewer seats than the original), Dodger Stadium will become the largest ballpark in MLB. But by the time the A’s new stadium opens in lovely Fremont in 2012 Major League Baseball stadiums built since 2000 will be 10,000 seats smaller on average.

According to Silver the decreases are due in part  to a change in fan viewing habits.

When this subject came up at the Symposium on Statistics and Operations Research in Baseball that I attended last week, the counterargument put forward—most articulately by Alan Schwarz—was that the ballpark experience just isn’t all that important anymore. The home viewing experience has been significantly improved by innovations ranging from HDTV to MLB.tv. If fans can watch multiple games at the same time on their flatscreens, and follow their fantasy teams in the process, this may actually be more desirable than attending a game at the ballpark, irrespective of the price of the seats.