I did that five years ago after coming to the conclusion that the US didn't care about any of these abuses and that decades of surveillance state would go by without any improvement. I implored everyone that would listen to leave; I thought that was the end of it.
After Snowden proved me absolutely and indelibly wrong, I decided this week to come back.
These people operate in secret because they can't justify their actions in a free and open debate. The secrecy has now been lifted.