Frustrated by low valuations and investor skepticism, Chinese companies are increasingly considering delisting from U.S. stock exchanges. Shanghai-based advertising firm Focus Media Holding's exit from the Nasdaq in May through a $3.5 billion buyout was the largest such departure to date. More of the 170-plus Chinese enterprises on U.S. exchanges plan to follow, says Hillel Cohn, a Los Angeles–based corporate attorney with law firm Morrison & Foerster who helped Shanghai-based conglomerate Fosun International, a 17 percent shareholder in Focus, with its portion of....