The 7 billion+ dollars that would be invested in the pipeline can be invested into other energy sources. This is not a renewable resource. Once the oil is gone, it is gone forever. In addition, drilling for and burning oil destroys many resources that rely on clean air & water.
It's been reported today(via huffpost Jan. 18th, 2013) that 18 top scientists are advising president Obama against approval.
Wind and solar power are going to be better investments in our children's futures as well as updating infrastructures to support them. This includes support for better mass transit systems, which will create jobs. As a personal note, I hope to see a climate committee that is publicly formed to advise the President on sustainability and its connection to the human spirituality & wellbeing.