Unfortunately gas/oil price is not dictated by the consumer but by commodities buyers. Mercantile exchanges is where the price per barrel is set. Yes supply/demand can still have an impact.
However suits with no infrastructure and no company save the investment house they work for/own buy and sell tanker fulls of crude daily/hourly. The buy low sell high thing. But since they do not actually have to transport/store their purchase they do not get financially impacted by their so called purchase/sale.
Changing this fundamental way of commodities exchange is how to change how gas prices are manipulated. I've seen instances when the OPEC's of the world increased production to keep downward pressure on oil prices only to have it rise significantly anyway.
Someone much smarter than me needs to figure out a way to punish commodities price manipulators. Oil companies are not the sole culprits, although they are complicit in this behavior. Investment houses are the real bandits. We constantly get fubar'd by Enron, AIG, Madof, etc and still believe these are isolated. They are not. This is a mentality which has worked it's way into business mentality. Money for money's sake who cares what we are doing to tomorrow as long as i get my money now. Pride in ones self, work ethic, morality, these have become just words, most westerners use the words but don't really live by them.
WARNING; small tangent below!
The proposed idea of not buying from the big suppliers is nice in theory except we as the end user do not know where say Canadian Tire gas bar fuel comes from. Could be the big 2 anyway and you are not impacting them at all by getting it from there.
If consumers are to have a real impact on the price of fuel then demand from us to politicians, car companies, etc. on much greater fuel efficiency is the key. Movement to something other than 'burning fuel' is also going to have an impact.
Ford has implemented the 'ECO boost' as a small attempt at appeasing us to get fuel efficiency. However direct injected turbo engines have been around forever, this is not new technology.... While i like that they made an effort, it a cursory effort at best.
Real technology shift needs to occur... to what I'm not sure. However using and engine perfected in the 1950's and giving a marketing spin (ECO Boost) is not the route to go. Except FORD's the only trying anything really.
Just my 2 cents. Blame my Mom for making me this way