One of the main problems ISP's have seems to be the amount of time/money which comes from tying up the server with downloads for music files. It can and if popular enough use up most of their bandwidth, which is measured in Megabytes per hour. Some ISP's have taken to restricting the amount of download size/time for each customer per hour. With the advent of the MP3 and WAV and RA files audio downloads seems to have overtaken the online Porn market.