Pete, I would agree that this is a reasonable solution, as long as a full list of the members (including the GM) is listed in the channel for everyone to see.
Imagine for a moment, that a beginning GM decides to run some campaigns here, and he or she isn't that great at it yet, but they have room for growth, they will get better with time. Now imagine, in this beginning GMs game , that the players think the GMs campaign sucks, whether it does or not is besides the point. It is human nature to express negative feeling like this, and the players would probably use whispers or what they believe to be a secret channel away from the GMs eyes, to either make fun of or in some other way bash on his campaign.
I am not saying that everyone is like this, but we can all attest to the fact that there are many jerks out there. How do you suppose that GM , new to gaming is going to feel, when he/she reads the negative comments about their campaign. Hopefully they shrug it off and find new players , but what if the negativity sours them to gaming all together. I know I would be more than a little upset to find someone spouting off negative comments about my campaign, heck , I get harassed in other forums for offering a free e-zine that is supposed to help people with different facets of their games.
It is not my wish to keep the GM in the dark, but merely to protect the GM and the players. Secrecy is a normal thing around the table, like you said one PC wanting to steal from another, or secret alliances and what have you. Most of the time, I don't make any efforts to keeps secrets from the GM, but sometimes circumstances call for it.
So long as everyone is aware of whom they are talking to inside of chat, I see no problem with Pete's solution.