LOS ANGELES (Reuters) – The explosion of electronic dance music in the U.S. has thrust DJs into the spotlight, but with great power comes great responsibility as they strive to stay fresh and maintain quality as demand for their skills rise. Electronic dance music has become a dominant force in the 2012 popular music charts, as mainstream artists such as R&B singers Rihanna and Usher, hip hop singer Nicki Minaj, and the ‘Queen of Pop’ Madonna have embraced club-heavy beats, often working with top DJs such as David Guetta. …