It is akin to aristocracy, but rather than nobility, it's money that rules. Giant coroprations with the means to essentially buy elections and in the end "get what they want"; which is usually more money, less oversight, etc. At it's base the entire system is driven by greed, hence 'Greedy-ocracy'.
The first well known use of the word was in the lyrics to the 1999 song "The Decline" written by Fat Mike of the band NOFX.
It also appeared around 2007 in graffiti caught on photograph around Quebec city (Canada)
It also appears in the lyrics of the song "The Broken Branches" by Star Fucking Hipsters on their 2011 album "From the Dumpster to the Grave"
Human nature, mans destiny
Blame it on the greediocracy
NOFX - The Decline