File sharing is legal. LW is a company developing a legal tool, and many use it to share legitimate files. Safari and Internet Explorer are legal, but some pages can show content that is illegal in some contries.
Telephones and computers are legal. Some people use telephones and telephones for illegal purposes.
Bottom line?--don't share files that shouldn't be shared. The stupid thing is that you can't easily tell which files are "infringing"
See
http://www.boycott-riaa.com/ for some lists of files that shouldn't be shared