This is a really great analysis of the current and past food spikes. Not something I can really summarize, so I encourage you to take a look at the full report. It is definitely worth it.
Of course, the part that I’m always interested in:
Thus, while the expansion of biofuels was an important factor underlying the general rise of food commodity prices in 2002-06 and their movement to a higher plane, it is less clear how much additional impact biofuels had during the subsequent 2007-08 spike in prices, as evidenced by biofuels’ continued and
growing presence through both the upside and downside of the spike