The government manipulates a myriad of markets. Obviously FX and Treasuries for starters, gold and oil via management of their own inventories and possibly from time to time index futures. One only need witness the Fed's shameless manipulation of auctions including the one last August when they purchased 7 billion in securities. The effects of said interest rate manipulation have an ipso facto effect on share prices. By effectively setting a ceiling on long bond yields, stocks are allowed room to grow in an artificially low rate environment.
Quote from Martinghoul:
I agree... See my response to JamesVU. I suppose we're gonna have to reach a consensus on the definition of "market manipulation".