Greed (Avarice) is the desire for material gain. It is similar to Gluttony and Envy, but gain rather than consumption or possession is key. Aquinas condemned Greed because "it is a sin directly against one's neighbor, since one man cannot over-abound in external riches, without another man lacking them...it is a sin against God, just as all mortal sins, inasmuch as man condemns things eternal for the sake of temporal things."
Religious authorities today seem to rarely condemn how the rich in the capitalist (and Christian) West possess much while the poor (in both the West and elsewhere) possess little. This may be because greed in various forms is as basis for modern capitalist economics upon which Western society is based and Christian churches today are thoroughly integrated into that system. Serious, sustained criticism of greed would ultimately lead to sustained criticism of capitalism, and few Christian churches appear to be willing to take the risks that would come with such a stance.
Consider, for example, the close political connections between capitalist leaders and conservative Christians in the Republican Party. What would happen to this alliance if conservative Christians began condemning greed and gluttony with the same fervor they currently direct against lust? Opposing greed and capitalism would make Christians counter-cultural in an way they haven't been since their earliest history and it's unlikely that they would turn against the financial resources the feed them and keep them so fat and powerful today. Many Christians today, especially conservative Christians, try to paint themselves and their conservative movement as "counter-cultural," but ultimately their alliance with social, political, and economic conservatives only serves to bolster the foundations of Western culture.
Greedy people, those guilty of committing the deadly sin of greed, will be punished in hell by being boiled alive in oil for all eternity. I don't see a connection between the sin of greed and the punishment of being boiled in oil, unless of course they are being boiled in rare, expensive oil. In that case, maybe it serves them right.
This image appeared in 1496 in Le grant kalendrier des Bergiers, published by Nicolas le Rouge in Troyes, France.
Further Reading: Greed: The Seven Deadly Sins, by Phyllis A. Tickle