[Daveinyork]

Forgot to mention government regulation which makes it too expensive for smaller companies.

[thackney]

Pretty tough to make that claim when several small indepent refineries are still in operation.

http://www.goodwayrefining.com/

http://www.crossoil.com/history_c.php

http://www.lundaythagard.com/

http://www.lionoil.com/

http://www.continentalrefiningco.com/

http://www.huntrefining.com/RefiningOps.aspx

http://www.wnr.com/Index.aspx

http://www.hollyfrontier.com/

More at:
http://www.eia.gov/petroleum/refinerycapacity/table3.pdf