Have you ever wondered about this? It seems like a pretty valid question to me. If the Bible says that Satan kills, steals, and destroys, then why does God allow him to continue to roam the earth and cause so much trouble?

Well, first of all, simple answers to really significant questions always bug me. So my disclaimer here is that this isn't "The Answer" to such a profound and important question... just some food for thought from "Life As A Vapor", by John Piper.

He starts by stating the question and proving, with scripture, that it is a valid one.

Then he says,

"Why then does God tolerate Satan? The key is that God aims to defeat Satan in a way that glorifies not only His power, but also the superior beauty and worth and desirability of His Son over Satan."

wow... imagine John Piper saying something like that :0)

He goes on to say:

"(For God to simply snuff out Satan) would not display so clearly the superior worth of Jesus over Satan. That will be displayed as Christ defeats Satan by His death and then by winning allegiance from the saints because of His superior truth and beauty above the ugliness and lies of Satan.
...Satan is a defeated foe... Christ has triumphed over him, not yet by casting him into hell and nullifying his influence on earth, but by letting him live and watch while millions of saints find forgiveness for their sins and turn their back on Satan because of the greater glory of Christ."

"If Christ obliterated all demons now (which He could do), His sheer power would be seen as glorious, but His superior beauty and worth would not shine so brightly as when God's people renounce the promises of Satan, trust in Christ's blood and righteousness, and take pleasure in the greater glory of Jesus over Satan."

"Therefore, take up arms and defeat the devil by being bold and glad in the superior glory of the Son of God!"

"Christ's superior beauty over Satan and sin is seen best when we are willing to suffer because we have tasted it and want to share it. One of the greatest blows against the power of darkness comes from the blood of the martyrs."

Some food for thought for ya...