Krugman is pretty damned harsh about biofuels, much as Time magazine was. Let's hope this is an overreaction and something can be salvaged.
The Royal Society has come out with what looks to be an authoritative report which is available.
Meanwhile, a quintuple whammy of financial volatility, increased energy prices, competitive bidding with biofuels, bad weather and increased demand for meat in growing economies, of which the first three trace and arguably the fourth trace directly to government errors in the west and especially the US, has sent grain prices soaring, abruptly causing protectionism in poorer food exporting countries and severe stresses in poorer food importing countries.
Update: In the comments, AdamW points to a UN report that worldwide grain production is at record high levels. This would seem to eliminate direct effects of climate change (e.g., Australian drought) as a major factor in the present price spike.
I find it really interesting that China's increasing prosperity is leading to increased misery elsewhere. This is consistent with the idea that the switch to a zero-sum game has already started.