You know, this is actually one of my bigger problems with online tabletop: the inability to guarantee that the GM hears what the players say. Not to listen in about actual, honest to goodness private stuff, but consider the sheer number of ways NPCs have to eavesdrop on players - scrying. Listening bugs. Telepathy. Any number of instances require a GM to know what the players are talking about without telling them 'uh, hey, I need you to have your private chats public for the next, oh, 20 minutes or so'. The problem being, of course, the moment a player realizes that he or she was overheard by an NPC (often standing 5 feet away, while the PC discusses killing said for some imagined slight), they start opening private skype chats or the like. Not something you can do when sitting at an actual table - you can ACTUALLY whisper, but anything audible becomes detectable. And, admittedly, you can always just have the NPCs be a bit more prepared for whatever the PCs try, on the fly, but that's not exactly an ideal solution, since it denies them the ability to feed false information. Alas, the problems of online play.