I tend to James's side in this thorny debate (the ignoramus can but tend).
It does occur to me that higher-yield/longer-lasting crops (and I wholeheartedly agree with Mike that tomatoes ain't what they used to be - nor bacon, cheddar or capsicum - but how much of that is new production regimes and how much is it the tortured taste buds of a 41-year-old smoker?) are a bit like information in general. Hard to withold and therefore hard to control (possibly disastrously bad, but possibly decisively good). Monsanto would face a bit of PR flack if it suddenly found itself having to go in mob-handed to burn down Somalian crops or suing Mrs Enid Ramsbottom for those unauthorised broad beans discovered in her planter box. And that's after paying up the dosh for planter-box inspections in Bradford and faecal analyses in Somalia.
The cost of patent security is gonna be pretty formidable, anyway - and the higher that cost (for companies or customs police), the more likely a healthy trend to decommodification ... dare I suggest the forces of production undoing the relations that brought them forth?