Mark Zuckerberg's casual attire--ensembles usually include some combination of hoodie, drab t-shirt, jeans, and sneakers (formerly flip-flops)--has earned him the titles of "fashion icon" and "worst-dressed celebrity," depending on who you ask, and has shaped cultural perceptions about how young tech entrepreneurs dress. But on Thursday night, when Facebook's CEO joined other Silicon Valley executives to dine with President Obama at the home of venture capitalist John Doerr, it appears from White House photos that the billionaire actually donned a suit and white dress shirt for the occasion, though we can't tell what shoes he's wearing or whether he went so far as to put on a tie.

Here's our first bit of evidence:

In this second photo, President Obama has suspiciously blocked the angle we need to determine whether Zuckerberg is wearing a tie (is it just us, or does it appear that his collar is buttoned?). Steve Jobs, notably, didn't abandon his trademark turtleneck. Is Apple's CEO more principled about his fashion than Zuckerberg?

All of this makes us wonder: Did Zuckerberg fleetingly embrace business casual for a presidential visit, or is he cultivating a new look as Facebook enters the big time?