I would agree with Biodiversivist that many popular press articles and blogs are slopping in terms of talking about biofuels from food/feed crops vs ligno-cellulosic sources.  In fact lots of disinformation gets thrown around these days on this subject.  Yes, we will not get to the really significant contribution to environmental improvement until the ligno-cellulosic technology takes off (still a few years out), but at that point the hope becomes real.  We also have the opportunity to do it "right" in terms of working out GEP (good environmental practices) for the biofuel/materials crops and setting up a certification system to insure thats how it is done (like FSC for the forestry industry).

The one point that was lacking in the above referenced post is the fact that agricultural productivity has long been and will continue to rise so that the competition for fuel/food will not be as severe as some worry.  I'm not saying that there won't be any competition, but there are lots of ways for that to even be a good thing (e.g. less super cheap corn sweetener to help our kids get obese, maybe an end to first world subsidized cheap food that undercuts markets for developing nations, maybe even more grass-fed beef...).  

Steven Savage, Ph.D.

Steve Savage: agricultural productivity has long been and will continue to rise
I think there's a logical fallacy here.  Agricultural productivity in terms of output per unit of labor has risen, true.

However, productivity in terms of agricultural output per unit of energy has fallen dramatically.  Modern agriculture uses much more energy than traditional agriculture in the forms of oil (fuels, pesticides) and natural gas (fertilizer).

The outlook for energy-intensive agriculture does not look good, in a time when the cost of energy will be going up.  (Peak oil, peak natural gas, rising demand).