Anything that you implement will be akin to the copy-protection on DVDs: it will prevent the casual user from getting a copy, but anyone who has the technical savy will. The fact of the matter is that you're sending a stream of 1's and 0's that represent an mp3. There's nothing that prevents someone from just saving those 1's and 0's to her hard drive for future use.
The only easy day was yesterday
Re: (OT) Stream MP3 but prevent user from downloading