Studios are finding them more trouble than they're worth, especially with so many of the songs already available on iTunes. Sacha Baron Cohen's "Bruno" was filled with well-known rock tunes, but Universal decided not to put out a soundtrack. From The Wrap:

Not all soundtracks are tanking. "Hannah Montana: The Movie" went platinum in just two months, "Twilight" has sold 2.2 million copies since it hit the shelves in November 2008 and "Slumdog Millionaire" soared to number two on the Billboard albums chart after winning the Oscar. But gone forever are the days of "The Bodyguard," the best selling soundtrack of all time -- thanks to Whitney Houston's "I Will Always Love You" -- moving 17 million copies, "Top Gun" selling 9 million copies and the rootsy 8 million sales of "O Brother Where Art Thou."

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"Transformers: Revenge of the Fallen" is the highest grossing film of 2009 so far, having generated over $380 million in box office and over $809 million worldwide since its release on June 24. In years past, the soundtrack for a blockbuster like that would be flying off the shelves. But even with a new song by the popular Linkin Park, "New Divide," the album is all rusty parts, according to Chris Byerly, store manager of Amoeba Music on Sunset. "It's not doing well here," Byerly told TheWrap. "Whatever sales 'Transformers 2' did were driven by the single."