The Marcellus Shale rush is rooted in the region's superior economics. It's big and cheap to produce.
In fact, Laurent Key of Societe Generale in New York is quoted by Bloomberg as saying that $1.90--an incredibly low price--is the price at which dry gas goes from being profitable to unprofitable in the Marcellus.
By contrast, the gas price must be $3.20 in the Haynesville and Barnett shales for dry gas production to be profitable. See http://www.telegram.com/article/20120621/NEWS/106219795/1002/business.
At recent prices, gas producers lose money producing dry gas in Texas and Louisiana but make profits in Pennsylvania.
What does that mean? For one thing, Marcellus gas is uniquely valuable. For another, sustained prices below $2 will be needed to bust the Marcellus gas boom. That's just not going to happen.