It would be cool if Synthetic Biology advanced to the point where one could start hacking bacteria to synthesize THC ;-) One would order a few bacteria over the internet and have a THC factory in one's room. No need for marijuana plantations that can be spotted with evil remote sensing satellites. No need for a database that could be used against the consumers.
This is wild speculation, of course. I just wonder how the government will be able to enforce certain laws when citizens are able to synthesize chemicals on their own homes, for their own consumption.
As a total aside, this came up in an episode of Weeds - our hero Nancy Botwin managed to discourage her clients from purchasing medicinal marijuana just by suggesting that there was such a central db.