Hemp has been uses for thousands of years by mankind and until last century in the United States it was common place. Farmers could benefit easily cause it grows like a weed and needs no pesticide or fertilizer. There are many products that could be made from it that would support many new jobs and industries. We have no idea how it fits into our ecosystem because it has been exempt from environmental impact studies from the DEA.
Farmers in many states are ready to start growing it here in the U.S.. Farmers in Canada are now growing and profiting from it. Here is an example of fiber usage and benefits: http://www.youtube.com/watch?v=Jb9teCK_Hy4 Hemp oil was replaced with petroleum oil in paints after it was banned in the mid 1930's. Ben Franklin use hemp oil based ink. If we are trying to move from petroleum based products hemp is essential. It can be burned as a bio fuel if necessary.
One acre of hemp can save 4.1 acres of trees in fiber production. That statistic is from the USDA.
Birdseed used to contain 50% hempseed. The birds would eat those first. What impact did this have on bird health and appetite for pests?
Here is a video on hempcrete housing. Hundreds have been build in Europe and studies show the walls actually absorb CO2. http://bcove.me/mq4q659c
As a last resource, all backed by bibliography, please reference http://www.jackherer.com/thebook/chapter-two/