Signal sends to your whole address a message book that you are now on Signal, without asking first. You can opt out, but there is no advance warning to do so. Sign up and suddenly be deluged with people from the past saying "hi." Bad idea. Private? Private my tail assembly. I'd like to uninstall but a. Client wants me to use it. Hobson's choice... Taught me to ALWAYS check settings on new apps. I do not trust Signal.