Cory Doctorow is releasing his book online for free, the same day it is being 'published'.
On his site he gives the reasons why, as well as a great quote from Woody Guthrie:
"This song is Copyrighted in U.S., under Seal of Copyright #154085, for a period of 28 years, and anybody caught singin it without our permission, will be mighty good friends of ourn, cause we don't give a dern. Publish it. Write it. Sing it. Swing to it. Yodel it. We wrote it, that's all we wanted to do."