Spotify announced yesterday that they will continue to offer unlimited free listening in the US (with ads of course) indefinitely. Subscriptions in the US for their premium service have grown very rapidly in a very short period of time. They continue to take away marketshare from their competitors (mainly Rhapsody and Pandora).
"We’ve been so overwhelmed by the US response to Spotify that we’ve extended the honeymoon for unlimited free listening. Right now, if you’re a free user, you can continue to enjoy millions and millions of tracks without time limits, gimmicks or catches. It’s our way of saying thanks to the US!"