SoundCloud has grown into a near-ubiquitous platform for sound on the Internet. If you streamed audio in 2012—from a preview of Lou Reed’s album with Metallica to bird recordings on a nature lover’s blog—there’s a good chance that SoundCloud hosted and streamed it. That impact earns Alexander Ljung, 31, a place on this list. His Berlin-based company, which has more than 200 employees working across multiple offices across the world, keeps gaining momentum. he service has grown to more than 40 million users, reaching 200 million listeners a month. Its creators upload 12 hours of audio content every minute. In May it launched a redesign that adds social features and improves the comment system. That kind of growth has attracted serious investors. In January, the company announced an undisclosed round of funding led by venture capital heavyweight Kleiner Perkins Caufield & Byers and with the participation of GGV Capital. Mary Meeker, the former Morgan Stanley analyst and current partner at Kleiner Perkins, has a board observer seat on SoundCloud's board of directors.