Normally, talking is a free action. But sometimes it's important to enforce a limited communication channel. The heroes have 8 seconds before the bomb blows up, and that's only so much time to chat about the weather before getting on to the vital stuff about the supervillain's password scheme.

A way to enforce this in the game is to use a stopwatch and give the players the same amount of time to communicate before cutting them short and going ahead with the explosion or whatever. This can be a great way to ratchet up the tension but it can also—

Transcript

Obi-Wan: Luke, I need you to listen carefully. This is important.
Luke: I'm listening.
Obi-Wan: You must learn about the Force, learn to master it... before it masters you.
Obi-Wan: Uncontrolled, the Force can lead to a greater wealth of evil than you can possibly imagine.
Luke: I knew it!
Obi-Wan: There is one remaining Jedi Master. You must seek him out. He will teach you to control your powers.
Luke: Why can't you teach me? You're right here.
Obi-Wan: The natural state of the midi-chlorians is quiescent. It requires profound effort to manifest, even briefly.
R2-D2: Translation: 1d6 rounds per day.
Obi-Wan: His name is Yoda, and I'm willing to bet he's still on the planet Dagobah.
Obi-Wan: I may see you there...
GM: Obi-Wan fades away into the blowing snow.
Luke: Obi-Wan! Wait! Wait!!
Obi-Wan: {almost faded away} Sorry, I only rolled a 4...