I think Greed is only the big mistake in gambling.
Well greed is the most known thing that let people make mistakes because they get addicted to gambling because of that.
There is no end to the desire to have more of the endlessness of man's structure, those who are influenced by this sensation can never be at ease, can not be happy, they are self-centered; They give the greatest damage to them.
http://www.youtube.com/watch?v=vryqdsx5ad8&nr=1