I still think it's more complicated than a simple lack of food. For instance, there is no actual shortage of rice, just structural problems that prevent it from getting where it needs to go. It is not the case that less food is being grown than is needed. It is the case that the food distribution system is distorted by dumb government policies. There is also some hoarding by speculators.
Most famines are caused by distribution problems, not production problems.
Here's a less alarmist approach:
http://www.businessweek.com/globalbiz/content/apr2008/gb20080428_894449.htm?chan=top+news_top+news+index_global+businessWe are probably physically able to grow about twice as much food as we currently do, if not more, barring energy and political considerations. By the way, current population projections see the Earth peaking in about 2050. (One reason is that urban areas only see population growth due to influx from rural areas, and as more of the earth's population becomes urban, this acts as a natural check on growth. And wealthy countries have less population growth, and more third world countries are becoming wealthier.)
We *are* fucked, though, to the extent that even farm production relies on fossil fuels.
On the fossil fuels vs. biofuels point, it is a bit strange that some people think that biofuels could be a replacement for fossil fuels. With fossil fuels, it's like you're just walking around, gathering up energy sources nice and pre-made. Like nature's AA batteries. Of course, you can just build your own AA batteries, but that takes energy itself and will never be cheaper until nature's AAs are all gone.