Obama decided (for now) to stop the pipeline abomination that was to traverse the entire USA. Jim Jones (former Obama advisor) says that the decision is a blow to America's "energy security." He says with tighter supplies of oil globally the US will need the oil expensively blasted from the thick tar sands of Alberta.
But the decision is a bonus for the security of American citizens and the world from warmongers who want to start another profitable fight in the Middle East. With that pipeline they could start another such war and have Americans less affected once oil prices zoom from $100 up to $300/gallon. They could conduct a pain free war without fear of a citizen backlash. Of course everyone else globally would then suffer (although oil producing countries would profit). But when is that ever a first, political calculation.