It's not a broadcast keyboard issue, but quite similar...

I had my computer setup with a headset for vent and a webcam that sat unplugged 90% of the time. It was thrown in with some other equipment I bought and had no real purpose. Anyhow I'm logged into Vent, and I get a phone call, so I drop my headset and start talking, I'm on voice activated and the damn things still picking up my voice... so I flip the hardware microphones mute on the headset and for some reason the light on vent stayed green.

I figured what the hell, its probably some form of static in the headset so continue with my conversation... the phone calls from a guy in my guild, another officer. He's pissed about a guy who happens to be in ventrilo with me... I'm agreeing that this guys a real jackass at times, and is definitely out of line this time... I give a few other examples of why he's a dipshit, etc... meanwhile my screen in wow is blowing up with "HOT MIC" whispers from the other dozen guys in the channel with us... but I'm not reading that.

Anyhow, the guy we were badmouthing heard the whole thing and for the next few days was lividly pissed at us... after that, we noticed the behavior changed! Thankfully his overhearing our candid conversation got him to straighten up instead of bailing out!