We suggest watching the National Geographic special, "Years of Living Dangerously."
Most of the palm oil comes from Indonesia where they're burning rain forests to plant the trees that make palm oil. In the process, they're releasing millions of tons of CO2 into the atmosphere and they're killing all of the wildlife that gets in their way.
The cultivation of palm oil is an atrocity and it's in nearly all packaged and processed food in the grocery store. Read the label and if it has palm oil, don't buy it.
With that said, if you can find sustainably farmed palm oil, some argue it's actually better for the environment because it produces more per acre than other oil alternatives. I've yet to find any sustainably farmed palm oil, though. Hopefully it'll be more widely available soon. However, it's still not considered healthy.