Is the gold price being manipulated?  There are those who say no, while others say yes – notably The Gold Anti Trust Association (GATA) – and on balance it looks to an impartial observer (relatively) that the answer is probably in the affirmative.  But perhaps no more so than any other commodities and some stock prices.  There is a whole mammoth industry out there – the big banks, hedge funds etc. – whose whole purpose is to make money from money and the more you have in the first place the easier it is to do.  Not by producing anything useful, but through manipulation of prices through short selling in huge volumes to drive prices down, buying on the turn, allowing prices to rise back up, taking profits, then more short selling to drive prices down again and the cycle continues.
See http://www.mineweb.com/mineweb/view/mineweb/en/page72068?oid=107062&sn=Detail.