http://www.econbrowser.com/archives/2012/04/a_ban_on_oil_sp.html:
Here’s some good analysis comparing the oil and natural gas markets to question the theory that oil speculators are driving up oil prices. I am not opposed to tweaking the margin requirements for trading contracts but am opposed to attempts to exclude some market participants.
Ned "The Head" Ryerson 
If oil speculators are driving up the price of oil, are they also cratering the price of natural gas?
http://finance.yahoo.com/news/hedges-bust-airlines-hit-crude-194422293.html
Can you believe these speculators?!? Now they’re driving the price DOWN! When are they going to make up their minds???