The following quote is from an article inThe New York Times:

"Senator Elizabeth Warren has called for the breakup of big tech companies like Facebook. Regulators have opened investigations into Facebook's power in social networking. Even one of Facebook's own founders has laid out a case for why the company needs to be split up.

Now the world's biggest social network has started to modify its behavior in both pre-emptive and defensive ways to deal with those threats."

what kind of market structure is this and why?