Apple is clamping down on piracy by imposing restrictions on the way that music can be shared via the iTunes service.
ITunes service has been hugely popular since it launched
Changes to the service stop people listening across the internet to playlists of songs created by others.
The change was included in an iTunes software update that also fixed some bugs in the service.
ITunes users are divided over the changes, but some people have been heavily critical.
Apple's iTunes music store has become hugely popular since it was launched in May of this year and recorded about a million downloads in its first week.
Part of the reason for its popularity was the fact that it placed few restrictions on what people could do with the music they downloaded or ripped from their own collection of CDs.
The iTunes service allowed people to listen to almost any music collection that was sharing the same local computer network as they were.
Digital music players are becoming more popular
But clever iTunes users found a way to extend this local sharing across the internet using Apple's own Rendezvous software.
Details of how to tweak iTunes to make it share playlists over the internet, and allow people to record the songs being streamed, were published online.
The update for iTunes is intended to close this loophole and limit who can listen to a playlist.
"Rendezvous music sharing..., has been used by some in ways that have surprised and disappointed us," said Apple in a statement.
"Some people are taking advantage of it to stream music over the internet to people they do not even know," it added. "This was never the intent."
The change has been widely debated on discussion boards online as well as on sites such as Mac Central and Slashdot.
Many people have said the restrictions mean they will not upgrade to the latest version and that the change stops many legitimate uses of iTunes.
One angry user wrote on Slashdot: "The digital lifestyle is all about the fluidity of bits, the fact that all computers on the internet are, in some sense, in the same place, no matter where they're physically located."
Others were less outraged and said that, even with the change, the iTunes service imposed far fewer conditions on its users than many other online music services.