You're reducing your assumption to songs. There are many other things that are shared between people; pictures, homemade vieoes, music from newcomer bands or singers, documents, free ebooks, etc.
What LW actually does is to offer people a way to connect from one computer to another (or many others). That's the concept of the program. Basically, you could see the modern messengers (msn/yahoo) as P2P programs as well (though they might work in a different way).
Regarding what is legal and not, well, it depends on which country you live in. In some countries you can share your songs (which you own already via a legally bought CD) with me, if I also have the same CD legally bought. And in case I do not have the CD legally bought, then it is still me who breaks the law and not you.

I guess the whole PR hike about how the music industry tries to get people like you and me for sharing files, which "they say" are protected by copyright laws, has brought the reality out of proportion.
Limewire alone has some 2-3 million users all over the world. Do you really believe that it is possible for them to go after any and all......
Do not misunderstand my point of view; I do not encourage you to break any law. I just want to put things in the right angle.
In the end it will be you deciding whether to download a certain file. It will be you deciding on whether to share any number of files. And that's the way with everything in life. Like the one who tries to get around some tax payments by stating some information in his favoure (which might not be true). Or driving the car above the speed limit......
Then punishment should fit the crime; as well the possibility of being caught....(but that's my personal point of view and does not reflect the opinion of the board owners here).

I guess you got my point anyway....

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"Never Argue With An Idiot. They Will Drag You Down To Their Level, Then Beat You With Experience"