I realize that many agricultural companies sell their crops or livestock via futures contracts to manage the risks inherent to their industry. It seems to me that this kind of activity would be ubiquitous in agriculture. How common is it?
the CFTC publishes the amount of large players holding or writing contracts, you can infer with that http://www.cftc.gov/MarketReports/CommitmentsofTraders/index.htm
although I would be interested in knowing people's personal experience with actual farmers and the futures markets too