"Chilling effect" has always been a profound term for me, because I imagine the "cold" (numbness really) sensation a human body often senses when something truly awful (disembowlment/dismemberment) occurs. The body's way of protecting itself is to go "cold", and in many ways that's exactly the effect taking place here, as well.
There's also an undeniable part of this conversation that rarely gets addressed simultaneously, and I'd like to see it sussed out more in concert; what about the folks who are doing Evil in these private channels? It's unacceptable to me that TOR gets used for child pornography, and it's unacceptable to me that my government finds out I'm gay before I come out to my family.
I don't want to provide those who would do Evil any safety or quarter. I also want to give people a powerful shield to protect themselves against judgement and persecution from the public and sometimes the law.
We should talk about achieving both of these goals, but we generally don't.
About the first one, physical, what king of stupid incompetent secret service lets an entire terrorist organization train their people on physical training centers, physically dispatch them to their targets, get their hands on weapons and explosives, and successfully commits their crime, while doing nothing because they are really focused on breaking Tor?
Universal surveillance is not just useless for fighting terrorism, it's actually harmful, in several ways. And most of those apply to almost any use you can came up for it.
About the last one, digital - inside of your mind (that is, inside of the criminal mind), those people need help, not punishment. Stop punishing them and they'll seek you.
Now, the real problem is the second set, digital - real Evil. I have no good answer for those, but the surveillance people also lacks this answer, and are almost completely useless against that too. I'm not willing to accept an argument claiming that mass surveillance needs to exist so those people may start doing that work in the future, when they discover some way to do it.