Prayer is petition, intercession, adoration, and contemplation; great saints and mystics have agreed on this definition. To stop short at petition is to pray only in a crippled fashion. Further, such prayer encourages one of the faults which is most reprehended by spiritual instructors — turning to God without turning from Self.
A long time ago, I worked with a young woman who was a serious conservative Christian. One day when snow was expected, she told me that she didn't want to come to work the next day and that she would be praying hard for snow. The next day there was a huge snow dump over the entire East Coast.
I would later read in the paper that the large scale snowstorm killed 14 people across several states. (The American south is not much used to snow and gets it so rarely that being really ready for it is prohibitively expensive.)
To me, this woman praying for a deadly snowstorm raises a few questions, questions that assume, as they very concept of petitionary prayer does, that prayers can be answered:
--When we pray for something, do we have a duty to think about the consequences of what we are praying for? Or is that God's job?
--If the consequences are God's job, then what is the point of petitionary prayer in the first place since God is likely to endorse the best course of action no matter what you ask?