Q: Why am I prompted in Messages, FaceTime, and iCloud to enter my password?

I've had my account setup and in use for a long time in Messages, FaceTime, and iCloud.  Yesterday, after powering on my MacBook Pro and signing into my user account I was prompted for my password for all three services (Messages, FaceTime and iCloud).  I just clicked the Cancel button.  Today, the same behavior.  This time I entered my password each time I was prompted.

Nothing in my setup has changed.  So I'm puzzled as to what would prompt this to happen.