Shazam, the music identification service, has been used by over 50 million people worldwide

"Shazam, the world's leading mobile music discovery provider, today announced that more than 50 million people around the world have used the Shazam service, an increase of 15 million users since February of this year. The phenomenal milestone signifies just how popular the music discovery service has become which is now live in more than 150 countries. "
Source: Shazam press release, 14th October 2009