Inet says that it wasn't until April 2011 when Android 2.3.4 became available that the OS was really ready to embrace dual-core processors. Before that, you had Android devices shipping with dual-core power that was not being taken advantage of by the OS. Mike Bell, GM of Intel’s Mobile and Communications Group, says that the thread-scheduler on Android is not ready for multiple-core processors and in fact, the multiple-cores are actually a detriment for users. Bell says Intel's testing showed multiple-core processors running at a slower speed than single core. He adds that testing shows that adding a second core leads to current leakage and a low power threshold because of the size of the case. This means that there might not be any advantage to Android users using a multiple-core processor.
source: TheInquirer via PocketNow