Pardon me if someone already touched on this point. It seemed obvious to me but I didn't see it stated yet:
Greed involves taking things that you do not need in a manner that denies the access to things that others do need. The gross accumulation of TVs by Mr. Snyder, now approaching the net worth of Bulgaria, excessive as it is does not deny the acquisition of a telly to anyone else. Nor does it deny food or other necessities to others. In fact. Jimmy's television disorder is an actual economic stimulus increasing the profits and paychecks of store managers and sales clerks.
Ditto for Oprah: if she buys a lot of cars (I do not know the truth to this, but IF she does) then her wealth is turned back into the community and nation. Sometimes purchasing products will do more good than giving money to charity. In large-scale economics, greed is hard to pin down. Some corporate CEOs are greedy, I'm sure of it. But I can not say for sure which ones.
Greed is much more obvious in small-scale examples: the people who ran the 10k "fun run" at the Hyannis Marathon last spring, and took all the food (all the chowder, all the drinks, all the coffee, all the chips, and most of the bananas and bagels, eating a bunch, then taking multiple extras and packing them into their bags) before 3/4 of the marathoners even finished, thereby leaving my exhausted wife without any of the expected post-marathon goodies...
Those were some greedy b******s.