Why is there so much oil stored there? Well, because we're making more oil than the world needs. Why are we making more oil than the world needs? That is a complicated geopolitical question. But the simple answer is that commodity producers tend to be persistent: they reliably overproduce until the bust is bad enough to force people out of production and then things adjust. Normally, OPEC or a similar organization would get everyone at the table and production would be reduced, dammit, to get the price back up, however, ISIS and Russia both fund their governments with oil production so they are _not_ going to cut back and it is in everyone else's interests to keep the amount of money they get per barrel absolutely as low as possible. So the overproduction is somewhat politically driven, in that political measures to reduce overproduction are de-motivated. (We are making too much oil so that it is cheap so as to put the squeeze on people we don't like. Basically. Where "we" is a diverse group of countries with wildly variant interests that happen to agree on this one point.) Anyway. Extra oil goes somewhere, and Cushing is basically the place where you can park oil, that isn't an aging tanker parked in the North Sea somewhere. The gods of the internet have not yet turned off "cushing oil storage" in images search at google, so you can get a sense of what the place looks like that way. (They may yet do so -- a lot of people are also worried about other kinds of risks at Cushing.)
Now for some good news! For everyone except Shkreli. He's the guy you love to hate for jacking the price on some obscure drugs, and can never remember his name. He has finally been arrested.
Couldn't happen to a more deserving person!
I apologize for the lack of juicy zoning stories. Maybe I'll find some later today.