Even if you think blogs are boring, this guy has some good stuff to say about covetousness:
Covetousness is desiring something beyond what God has given me. At its core such desire is a challenge to God’s sovereign control over my life. I am saying that I think I know better than Him what is best for me to have. So I make an idol of whatever I covet and proudly challenge God all in one desirous moment.
The very scary thing about such a situation is that it is so similar to how our arch-enemy, Satan, fell (Isaiah 14:13). It is also exactly how Adam fell (Genesis 3:6). In both cases they were cast out of God’s presence and so too will I be if I nurture a covetous heart.