>>A few minutes ago I tried creating a message in Chatter to Kevin Goff with a link to a Washington Post article. Although it said his name in "To", it got posted to All.
>>
>>Then I tried a test message, it also got posted to All. Screen shot of what I had just prior to hitting the Send button is attached as an image.
>>
>>Although I tried to send this message to Michel Fournier I suspect it will end up addressed to All as well.
>>
>>UPDATE: yep, went to All instead of MF.
>
>I suspect that you have misunderstood the concept here. If you're a subscriber, you can sent private messages using the Private button. When you make a "normal" thread addressed to a specific member, you only hint to others that although the message is for NN, while everyone else can read and reply if they want.

You don't have to be a subscriber to send private messages. Anyone can do this.