The Sons of Liberty, and other groups and individuals active prior to the Revolution, maintained their anonymity by posting letters on trees and bulletin boards, meeting in dark wayside taverns and such. Eventually those patriots had to come out of the shadows and work in public to unite enough people to win our freedom.
Anonymity is like protecting your car from theft. No matter what you do, if they really, really want it, they are gonna get it. Heck, if the stakes are high enough, you can get data off a BROKEN hard drive.
My goal is for my identity to not be that desirable. ;)