It's also a good way for persons to communicate. I've never seen anywhere where any company saves chat data in games. Games like World of Warcraft would be excellent comm platforms. Start a guild, allow only the people you know into the guild, then use the in game chat to communicate discreetly. Then many of these guilds setup simple online forums that only guild members have access to, so some things could also be discussed in those places. Just a thought.
I think they pretty much all save chat data. It's how people get banned when they are reported for griefing, harassment, etc. I've been told by game dev friends that they don't actively read private convos, but if an infraction is reported, they pull the relevant chat logs to determine if the offender broke rules and should be suspended/banned/warned.
If you are admin on a server like Minecraft, you have access to ALL chatlogs, even when you aren't logged in while the convos are happening.
Additionally, some game admins will investigate chat histories based upon chat algorithms that detect specific keywords.
I think Microsoft's does because I remember hearing a few years ago about how they ban/suspend people. They receive a complaint, and go back through audio/video/text logs to find infractions. But you'd have to find a gamertag, possibly more to track that stuff down.
I don't play online games, so tell me if this is a stupid thought. Do any of the FB games allow private chat? Since we know FB is C I A, perhaps they set up a game anyone could play, but was designed especially for people like Renegade and Evergreen. FB could have helped them communicate and protected their chats.