"You haven't said anything," Musk once said in a meeting, according to a former SpaceX employee. "Why are you in here?" NTB Scanpix/Heiko Junge/via REUTERS Most people don't like to have their time wasted with unnecessary meetings.

But Elon Musk, the founder and CEO of SpaceX, has a strategy to keep things moving, a former SpaceX employee posted on Quora.

The former employee relayed a story where Musk once called out an employee in a meeting. He wrote:

"One of my close friends started there a couple years before me. He worked (and still does) in an analysis group, so meetings made less sense when you could just walk over and ask someone a question. He told me a story one time (this is paraphrased):

"Elon to a meeting member: 'You haven't said anything. Why are you in here?'"

The former employee further explained Musk's rationale for making such a blunt proclamation.

"That may be borderline rude, but it makes sense," he wrote. "Don't be in a meeting unless there's a purpose for it; either to make a decision, or get people up to speed. In most cases, an email will suffice."

Musk isn't the only CEO who values running an efficient meeting — Jeff Bezos, the Amazon founder and CEO, employs the "two-pizza rule" to cut down on meeting bloat.

His thinking is simple: Meetings should be small enough that two pizzas would feed the entire group. If not, the meeting would probably be too big and unproductive.

Bezos also told Fortune in 2012 that some meetings with senior executives began with silent reading time, during which all attendees familiarized themselves with a memo describing the matter at hand, took notes, and mulled over the issues before beginning the discussion. That way, he said, he gets everyone's attention immediately — because no one likes to waste time in a conference room.