Pandora rival iHeartRadio hits 50 million user milestone

iHeartRadio, the online radio service from terrestrial radio giant Clear Channel, has hit 50 million registered users, a milestone only three years in the making.

The pace of iHeart signups — faster than that of rival Pandora, the biggest radio provider on the Web, as well as Twitter and Facebook — reflects the growing popularity of streaming music as well as the promotional heft that comes from a giant like Clear Channel as the parent of the developing service.