I used to believe in God. Then I went through some really tough times, saw my family go through some tough things, without reason. Ten years later, we have not fully recovered. I refuse to believe that God would intentionally cause his creations pain and suffering, simply for the pleasure of watching them fall apart. I understand that there are those who say that God tests us and our faith in him, but to be honest, it's a really shitty thing for him to do. It would be like having a husband/wife who cheats on you, flaunts it around to see your reaction, and then when you get angry, says, "Oh, I was just trying to see if you love me enough to try to make it work after this." =/
Also: If God is omnipotent and all good, why does so much bad happen? I refuse to believe that God would create humans, knowing that they would oppress, persecute, and kill each other. For if each person is made in the image of God, wouldn't he take great offense to it? God would not condone such behavior, as it would be systematically killing part of God himself.
And why would God create a being that would ultimately end up destroying his other creations? Humans were (supposedly) created on the Sixth Day; we were the last. It is incomprehensible to me that God would knowingly put a being on his beautiful planet and then tell them to destroy it ("have dominion over nature and subdue it"), everything he made before us (well, besides the sun and moon). If it was not God's intention for humanity to destroy the planet and pollute the skies, then obviously he is not omnipotent; if he were, he would have known that it would happen.