SoundCloud has grown into a near-ubiquitous platform for sound on the Internet. If you've 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 it was hosted and streamed by SoundCloud. That sort of impact makes Alexander Ljung, 30, a clear choice for Billboard's 40 Under 40 list.
Ljung's Berlin-based company, which has more than 100 employees and offices in London and San Francisco, keeps gaining momentum. The service has grown to 20 million-plus users (adding 1.5 million per month right now); it had just 1.2 million in the summer of 2010. 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 participation of GGV Capital. Mary Meeker, the former Morgan Stanley analyst and current partner at Kleiner Perkins, now sits on SoundCloud's board of directors.