atalanta>"Another sidelight - where terrorists/freedom-fighters/islamists/rebels ( call them what you like) in places like Libya have taken over the oil fields, this move by OPEC may reduce their income ( and ability to buy weapons) significantly."
Good point atalanta, and I've not seen that idea anywhere else. ®
And good point EDDIE about one reason being Saudi punishing Russia for its Iran and Syria support; but your way off on Saudi reserves being so large and cost of Russian oil production:
"The oil production cost in producing fields in Russia ranges from $10-$16 per barrel. The oil production cost in new fields in Eastern Siberia is estimated $22-$26 a barrel.Middle East ranges $2-$5 a barrel."
http://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=5&cad=rja&uact=8&ved=0CDMQFjAE&url=http%3A%2F%2Fwww.petrofinder.com%2Fdealgate%2Fdown_load_deal.php%3Fdeal_no%3D258&ei=bNm8VIj6Fofdat-cgdgG&usg=AFQjCNFd8bhGROxwcVOmT3yfkWtgAQLScQ&bvm=bv.83829542,d.d2s
http://en.wikipedia.org/wiki/List_of_countries_by_proven_oil_reserves#Countries
The last paragraph of your Link probably tells us the real answer Hopkirk:
"It's human nature to speculate about the schemes of behind-the-scenes players when the stakes are so high. It can also be comforting - a much preferable alternative to a system where the health of nations is determined by the random permutations of fate and the chaotic fluctuations of an uncontrollable market."
Second decade of the 21st Century and the Foreign Exchange Markets, the Stock Markets and even 'market forces' are still untamed.
Thanks All who answered.