If you do a google image search- you see him wearing either a grey or brown facebook tee if he's not wearing a button down shirt. Is he taking a page from Steve Jobs?

ANSWER by Neel Hajare (Facebook Intern '11):

In one of the first Friday Q&As of Summer 2011 after the interns arrived, one intern asked for the mic and asked something like "Hey Zuck, me and a couple of the other new interns were wondering, do you have more than one shirt?"

The whole room (including Mark Zuckerberg) cracked up, but he went on to say that he wears the same clothes every day because he's busy and it makes for one less thing to think about in the morning.

Steve Jobs only wore black Issey Miyake turtlenecks and jeans. "both because of its daily convenience (the rationale he claimed) and its ability to convey a signature style." (from the Walter Isaacson biography).

Zuckerberg's comment about it being one less thing to think about backs up a theory I recently read about: "Decision fatigue-The more choices you make throughout the day, the harder each one becomes for your brain" –NYT nyti.ms/qsQDlV

When you think about how many decisions it must take to run a constantly evolving multi-billion dollar corporation, it's understandable not wanting to have to make one more about what to wear in the morning.

SOURCE: http://www.dwitch.com/queries/view/135/Why%20Does%20Mark%20Zuckerberg%20Always%20Wear%20The%20Same%20Shirt%3F