The Internet means exposure, and these days, unless you're in the Top 40, you're not getting on the radio. The Internet is the only outlet for many artists to be heard by an audience bigger than whoever shows up at a local coffeehouse. The Internet allows people like me to gain new fans; if only 10% of those downloading my music buy my records or come to my shows, I've just gained enough fans to fill Carnegie Hall twice over.
With the court's decision, the RIAA didn't just defeat Verizon, the Internet service provider that the RIAA sued. It damaged the viability of recording artists who don't conform to the mainstream musical tastes of the moment.
Do you like '50s-style acoustic folk? Big band music? European synth? If the decision stands, you'll have to rely on word of mouth to find it -- not the Internet. Because if you get hold of an "infringing" file, you may find yourself on the receiving end of a record company lawsuit too expensive for any individual to fight...
The RIAA says it is doing all this to make more money for me and other artists like me, but don't be fooled. Many musicians would lose money, many fans would be denied a universe of new choices and the possibilities of Internet music would be cut off before the revolution even begins.