Lavender, you were asking about downloading music, and why it is illegal. Thought I would start a separate post for it here.
The main reason d'ling music is illegal, unless through specific approved fee paying sites, is copyright protection. Every time a song is played, bought etc, a royalty has to be paid to the record company. By d'ling it, that is avoided. The sites online where music can be downloaded by file sharing are illegal, although many millions do it, because they are just copying tracks from one person to another, and avoiding paying anything to the record companies.
This link might help explain about royalties.
There has been a case in America recently, where a woman was fined $12,000 for illegally downloading music from the internet, in a case brought by the RIAA, this is copied and pasted from a site I found:
"The Recording Industry Association of America (RIAA) announced on June 25, 2003, that it will begin suing users of peer-to-peer (P2P) file-sharing systems within the next few weeks. According to the announcement, the RIAA will be targeting users who upload/share "substantial" amounts of copyrighted music. The RIAA has stated that it will choose who to sue by using software that scans users' publicly available P2P directories and then identifies the ISP of each user. Then, using the Digital Millennium Copyright Act (DMCA), the RIAA will subpoena the ISP for each user's name, address, and other personal information in order to sue that user."
Yes the record companies make and sell you mp3 players to play your downloaded tracks on, but they want you to go to one of their sites, register for a fee and download them legally.
It's a bit of a grey area in policing it though, as there are so many internet users worlwide, it seems impossible that they can control everyone, but it is illegal just the same. Noone would come online and openly admit to doing anything illegal on a website, I am sure, which is why your question about if anyone on mumsnet has done it has been left unanswered.
In answer to another of your questions, Napster was a big p2p website, which shared files worldwide. It was forced to close down, as it was illegal, and reopen as a legitimate fee paying site. Kazaa is a similar site, but on the illegal side of things, as is Emule. I know these things from dh being in the music business btw. Hope this helps.