Travis Kalanick and Mark Zuckerberg blow off steam at Drew Houston's ping-pong birthday party

Uber's CEO Travis Kalanick has been under a lot of pressure lately. So this past weekend, he took a night off and went out to celebrate Dropbox CEO Drew Houston's birthday. Oh, and Mark Zuckerberg was there too. We're not sure if they offered leadership advice, but we do know they played some pong.

Dropbox CEO Drew Houston celebrated his birthday party at Spin's "Babes and Balls" party last Friday night in San Francisco:

A relaxed moment for Uber CEO Travis Kalanick.

Kalanick and Houston teamed up for some doubles.

Facebook CEO Mark Zuckerberg also played. He looked pretty intense....

Maybe because he was playing table tennis Olympian Lily Zhang.

Nice backhand!

--Photos by Ryan Soule, used by permission