Supernatural began as a series immersed not only in small-town America but also in small-business America.  At the start of the Pilot John Winchester owned a garage, and Dean Winchester was uncomfortable in a suit in Phantom Traveller.  Big business was a far-off world which could be milked for what could be got through credit card fraud (Pilot, Faith), fake medical insurance (In My Time Of Dying) or bank robbery (Nightshifter). The Winchester's travelling lifestyle put them out of reach of any consequences of their frauds on the corporations: big business doesn't cope well with change and uncertainty on the scale of the Winchester's hunting lives.

In contrast to these arms-length dealings with remote big business, the businesses we do see first hand in the first three seasons of Supernatural are pretty small beer.  There's the property developer in Bugs (who is quite probably going out of business by the end of the episode), the cafe in Scarecrow, the motel in Something Wicked, the hotel in Playthings.   There's the Roadhouse, too, for a short while.  In this world, the greatest model of commercial success is the auction house in Provenance, a family owned single-site business.  Here, the camera pans across a line up of sparklingly clean luxury cars (including a Bentley) that ends with the mud-splattered Impala.  It's an effective demonstration that even this level of business success takes the Winchesters outside their normal setting.  Similarly, Bela runs her own one-woman business, but both the nature of her business and her very considerable financial success in it are a contradiction to everything in the lives of the Winchesters.  

Interestingly, many businesses in the media and entertainment industries are fitted into this model of small-scale and struggling businesses.  There's the local newspaper in Route 666, the christmas faire in A Very Supernatural Christmas, the Mystery Spot, the ghostfacers starting up in their parents' garage in Hell House, the small-time magicians in Cris Angel is a Douchebag, Chuck the writer of a remaindered series of books in The Monster at the End of This Book and The Real Ghostbusters, and the wax museum owner in Fallen Idols who is hoping to attract the young crowd.  The circus in Everybody Loves a Clown and the film company in Hollywood Babylon are more successful, but still not top-rank (only Dean in geek mode recognises any of the actors in Hell Hazers II: The Reckoning), and the telephone company in Long-Distance Call is hardly shown as a business at all, just a place of work.  The churches we see (possibly as another branch of the entertainment industry?) are also small-scale or struggling: the tent in the field in Faith and the church in a run-down location in Houses of the Holy.

The first sign of change in the pattern of only showing small businesses comes towards the end of Season 4, in It's A Terrible Life.  Sandover Bridge and Iron Inc. is definitely very big business.  It has a large Tech Support team crammed into those small cubicles.  It has an HR department on floor 22 of a building that started out as 14 floors and is apparently still occupied by only the one company.  An article on PT Sandover, researched by Sam and Dean as they watch the Ghostfacer's video for hints and tips, refers to Sandover "dominating the industry with the scale and scope of its projects."  When Dean's boss Mr Adler is revealed at the end of the episode to be the angel Zachariah, he makes it clear that Sandover Bridge and Iron Inc is real: "real place, real haunting".  It's corporate America, appropriated by the angels for their own purposes.

After It's A Terrible Life the angels gradually reveal themselves as not only being willing to make use of corporate America, but also as being themselves organised along the lines of a big business. There's an extensive hierarchy, and in It's a Terrible Life Zachariah is disdainful that he has had to come down to earth himself, into a smelly meat suit, rather than being able to leave everything to his underlings.  In Dark Side of the Moon, Zachariah is clearly in corporate-man mode.  He's cleared his schedule in order to brass-tack the problem of Dean's consent so that he can get back on the fast track to employee of the month.  He used to walk the halls and people would avert their eyes, he had respect.  Now everyone is laughing at him because he can't close the deal.  His response to Joshua's unwelcome interruption is classic corporatese: "I'm in a meeting".   That Zachariah is acting as a company man becomes particularly notable at the start of Point of No Return.  Zachariah drinking in the bar is a corporate executive who's been pink-slipped for being unable to nail the bottom line by sealing the deal of the millenium.  He is delighted when he's called back to the business.

The angel's use of corporate America is neatly balanced in The Devil You Know, where we learn that demons also find that it's a good place in which to further their aims.   The demons have their own equivalent of Sandover Bridge and Iron but take it one step further.  The demons are using the pharmaceutical company Niveus to create and spread the Croatoan virus.  Distribution of the virus on the scale planned is beyond the capacity of the demons when acting only through possessed humans.  They can only acheive their ends by making use of the systems already put in place by humans.  At Niveus the demon Brady talks about meetings and appointments just like corporate man, but memorably makes the metaphorically cut-throat world of upper management all too literal.

Whether it's angels or demons running the company, being a junior employee in a big corporation is presented as less than life-enhancing, as Sam discovers in his cubicle in Its A Terrible Life.  It's fatal for the employees killed by the ghost of PT Sandover.  In other episodes, being a junior employee is hard on Zachariah's sidekick angels, all dressed in regulation business wear, who have a high likelihood of being banished or killed, as in Sympathy for the Devil and Point of No Return.  At Niveus junior employee status is fatal for the laboratory workers who are used to test the Croatoan virus and for Mitchell, the employee who needs to "do the best of someone better" and whose throat is cut by Brady in order to provide the blood for a chalice call to Pestilence.  In Season 4 Castiel himself, as a junior representative of the angels, is sent for a punishing period of retraining when he starts to query the company line set by his superiors in the organisation and the means he is required to use to achieve their objectives.

Corporate America is of course currently going through its own apocalypse, with the credit crunch starting in autumn 2007 and the Wall Street banking crisis in autumn 2008, so it is particularly appropriate that corporate America should become both the model and the means through which angels and demons play out their roles in the apocalypse.  It is interesting that  Eric Kripke said in an audio interview http://scifitvzone.com/2009/10/06/supernatural-the-wal-mart-apocalypse-an-audio-interview-with-eric-kripke/ before the start of Season 5 that this would be "the Wal-Mart apocalypse".   At the time he said this, Kripke was talking specifically about budgetary constraints.  But did he also, consciously or unconsciously, also mean that this would be the "big business" apocalypse?   The credit crunch and banking crisis have imposed devastating and uncontrollable consequences on individuals who have no responsibility for the cause of them and no means to prevent them.   The Supernatural apocalypse too is being played out between the corporate monoliths of the angels and demons, with humans as the powerless victims of decisions made far away by unaccountable organisations.  As a commentary on our times, one can only hope that the resolution found by Sam and Dean Winchester, with the motley band of helpers they have assembled on their way, provides a quicker and more satisfactory end to the Supernatural apocalypse than seems likely for the current real life financial crisis.