You joke but I can totally imagine a future where there are embedded sensors in the bread that transmit local conditions and (after ingestion) health/medical data.
Such a loaf could be given away free if the data collected could be repackaged and access to it sold to the highest bidder (I'm thinking pharma companies might pay).
A (imho insidious) way to get this accepted by the public would be to target humanitarian efforts first. Tracking health and disease in refugee populations is a real problem, so this system could offer tangible benefits. The refugees aren't really in a position to complain about privacy aspects and it'd be unpalatable for anyone to try a cost/benefit analysis when considering immediate survival against future privacy concerns (esp when it's framed from the point of view of saving a child -- as it usually is). Once this is considered 'normal' in such situations, it could be a short hop (or slippery slope?) to the supermarket.
If you think this is ridiculous, please remember that there was once a time when having robots read our email was considered hugely invasive by much of the public (Gmail launch).
I have an idea for a novel about this, I'm just not a good writer.
Basically, you ingest food and something in it collects data and can show you advertisements (or whatever) based on your eating habits. You wouldn't even have to know you've eaten the stuff (the nano-machines or whatever) but you'd start seeing ads because the nano-machines have attached themselves to your eyes and are creating images for you to see. How do you know what's real, then?
We don't have that technology yet (AFAIK), but this is just one step beyond a few current technologies (Google Glass + nano-machines?) and an extension of the path of privacy invasion via technology we're currently on.
This might just sound like crazy science fiction paranoia but I'm pretty sure we'll see something like this happen in the next 100 years.
