Mine idea was to create olygopoly. Group of traders, which will work in one direction and create profit to each other.
Plan:
1) collect about 100 active people, which will follow the plan.
2) create desinformation on the market. 100 people just go to different servers, groups, tf2outpost.com, etc. and just tell everyone that key is falling. ( not only tell, but actually buy it for lower price. For example: "As all of us know keys are falling nowdays i am buying them for n ref" )
3)Due to passion and greed of individual players, we would be able to make fool out of the market for some time and get keys for lower price. (When everyone tell you that key is falling in price, you will belive it yourself, because you do not know that it is organized, so number of people working for us will increase even if they wont understand what they are actually doing.)
4) we buy keys for short-term low price
5) stop
6) key price rise
7) we sell it.
8) go to step 2

However after all i understand some problems of this plan.
1) Hard to collect people for this.
2) Hard to keep in secret.
3) Too many agents, so there is possibility for deviation from common derection
4) Steam community market is too large for 100 people. Perfect information exist in market and such action can be ineffective.
5) power is in hands of sellers. 3000 keys supply against 130000 demand. This plan is going be impossible until community market will stop exchanging keys. Because nobody will buy keys from steam, if they can buy it from community market for chipper price. It causes luck of keys in whole market.