“There’s a clear trend toward white box — getting away from the model where everything comes pre-integrated from one vendor,” says Guido Appenzeller, Big Switch’s CEO. Any of the “hyperscale” Web/cloud players — the likes of Google, Facebook, Amazon Web Services LLC — have “at least tried out white boxes in the data center,” he says.

via Light Reading – Intel Invests in Big Switch.

This is the first I heard of the term white box.  The article is very informative.  Here’s one more blurb that may help describe it better:

“You will see some of the largest customers in the world demanding some very specific mandates, one of which is standardization, which implies white boxes,” says Jason Matlof, Big Switch’s vice president of marketing.

The bottom line:  The largest customers want open standards  — probably to create a more competitive marketplace for the massive amount of boxes they need to buy.  More competition = lower prices or better features or simply lower total cost of ownership.