fireflights:
Problem with that tyr is if it's a large enough game like mine is those private groups get eaten up fast and hot enough of them for everyone.
Sure, but it takes about... 7 people, give or take (depending on whether or not you start doing groups of three), before you start running dry. And that's assuming everyone actually needs a PM thread with every other player. But every workaround has problems.
You can use the honor system. Or you can use the groups. Or you can build another game. Or you can use an outside communication source. Or... you get the picture.
In the end though, it's just one possible solution. If it doesn't work for your particular game/players/you, don't use it. ;)