Many millions of prayers are offered up to God each day. Some of the prayers reach him, but the vast majority do not, at least not directly. The God I serve wants the world to know to whom they are praying so that there is no deception.
When a prayer is offered up to God, one of three things can happen. Either it is intercepted by Satan, it is answered indirectly by God, or it is answered directly by God. When it is intercepted by Satan, anything is possible, including him answering the prayer, if it suits his purposes to do so. His ultimate purpose always is to kill, steal and destroy. The vast majority of prayers, including prayers that seek good and positive things, are intercepted by Satan. If you are praying that evil circumstances visit someone else, you should know that those prayers never reach God and always are intercepted by Satan.
Prayers to God are supposed to be a methodology for confidently appropriating the powers within you to accomplish any desire that is in accordance with God's will. Our human spirit is relatively powerless against the forces of darkness. There is no genuine overcoming, Godly power inside of you if you do not have God's indwelling Holy Spirit. With the indwelling Holy Spirit, he becomes your source of power to teach, guide and protect you as you learn to take authority over the forces of darkness and evil that inhabit our world.
God also answers prayers indirectly. In this instance, he becomes aware that a prayer is being offered, eavesdrops on the prayer, then directs his Holy Spirit to answer the prayer as appropriate. If someone does not have the indwelling Holy Spirit, this is generally the methodology by which their prayers are answered and many people have had their prayers answered in this manner. However, it is not God's ideal because the person never comes to a knowledge of the truth that they can have God's power and authority operating on the inside of them at every moment of every day. God wants to establish his throne in your heart so that you will know that the kingdom of heaven is within you.