Abandonware is software that is now unsupported by the people who originally made it. The term was coined for the Gaming industry for games that - due to the shifting sands of publishers and developers - are no longer either owned or acknowledged by the people who originally created them. There are spots in the darkness, Stuff like Elite - which is still being argued over today, and there are also black holes: Stuff like the ancient Atari games (Pong, Space Invaders, Centipede, etc.) which were bought by Hasbro  and turned into Spinny-Rotaty-Neatocool 3D versions. Which were crap. But I digress. There are games that have fallen out of the back catalogue. Like Lemmings 2, originally created by DMA Design for Psygnosis was lost when Psygnosis were bought by Sony. You cannot and will not find this game supported anywhere, because DMA are on to GTA3 and their new bits and are no longer affiliated with Psygnosis (Who own Lemmings, AFAIK), and Psygnosis no longer acknowledge it because it is no longer part of their structure. Vanished.
So people who have the game put it online. There is no way Psygnosis would make money from it anyway, because they don't support it anymore, and there are no new productions. People who want these games actually want these games. But Copyright law means that you can't distribute it unless you are given permission to by the creator/owner. This is why I support (From a distance - I've never actually used it) things like Freeloader, which allows you to download (fairly recent) games in return for eyeballing a few adverts, and I also occasionally trawl the Abandonware sites when - in a fit of nostalgia - I want to play some old game I lost the disks for ages ago, Or owned the Amiga version of, or always wanted to play. I'm digressing again.
To sum up the above paragraph, Abandonware Good. So why Napster Good?
Napster is (was) a fantastic source of the musical equivalent of Abandonware, stuff you would never ever buy, or possibly even find, but could now listen too. Unfortunately with the technology was the ability to put everything online, including all the stuff the record companies are selling in stores up and down the country, across the world. and including the stuff that is actually making artists money. This is coming into the Information Wants To Be Free argument, which is another rant in the brewing, which states that the important thing is the creation of the information or the art, The payment is secondary. Unfortunately it's a necessary secondary, In order to continue the Art you must feed, clothe and house yourself and those dependant on you for food, clothing and shelter, and in the society we live in you cannot do this. Artists and Information Gatherers alike require sponsorship of activities. And if you are giving away for free what they need to sell for money, then you maybe are depriving the future, because they may be forced to give up and do something that actually pays.
Like web design.
(Hint, Do I want to sell my soul? No. In an ideal world, I'd write for a living, or invent websites, Or combine the two and get paid for Aquarionics. This is not an ideal world, so I am job hunting)
This started with Napster, so it goes back. The tracks I have downloaded Napster have been:
Of the above, I have bought the two TMBG albums that contain the tracks I downloaded and the entire TL back catalogue. Some of the Random Whims I would like to buy the albums for but can't because they don't sell/ship them here, some were just random things I wanted to hear again. None of the tracks I haven't bought are things I would actually pay for, usually because they are single tracks from entire albums/box-sets, and not even I will spend £15 on a CD for one track. Unless it's a very good track.
And that's what Napster is good for, the Abandonware tracks you can't get in the shops or at all. But the technology lead to the other stuff coming as well, and so it had to go.
For the record, if Napster were to start charging $10/month or something for the service, I'd be happy to pay. I'd have to give up paying for Ultima Online, but it'd be worth it.
The record companies hit Napster with the large blunt instrument of Law, when the laser-guided precision of negotiation would have been preferable. Napster will die, and 100s of other similar systems will spring up, and have done. But that isn't the point. Lawyers take great delight in playing Whack-a-mole with copycats to the outlawed systems. There needs to be an "official" Napster. And it'd be great if the people who ran the old one could do the Official one, since it worked so well. But they won't. The Record companies are announcing their own Online Music Emporiums, another thing that misses the point entirely, since the whole point of Napster (or even the entire Music Retail industry) is that you can go to one shop and buy from many record labels. You don't need to know that the Divine Comedy are now published by Parlophone and go to their record shop, you just head down to HMV and look under "D". United, the system could stand. Divided it will never get up, let alone fall.
The Music industry needs something like Project Gutenberg, where old music can go to die where everyone can remember it.
 Not strictly true, in fact. Atari's games catalogue was bought by Activision (Also holders of Zork and the rest of Infocom's games) who sold it to Hasbro, who have themselves recently sold their Computer Gaming arm, leaving several new games in trouble.