I'm still waiting for someone to send a take-down notice to ToS's on major platforms. That'll be entertaining.
I suppose at the end of the day, everyone receiving nastygrams could have a contract with AWS that prohibits disclosing the names of talks at their conference. That is a shitty condition to attach to a cloud service and should not be legal, but it probably is. (I wonder what speech conditions I agree to for receiving electricity at my house. I've never checked.)