The sheriff's deputies found one plant.
One. That's not enough to sustain any amount of trafficking; hell, it's probably not enough to sustain anything more than a very light personal marijuana habit.
The fact is that the fully illicit marijuana market in the US is mostly in the hands of the Mexican cartels. By "fully illicit" I mean cannabis not cultivated by "mom 'n' pop" growers in states that permit cultivation and use of marijuana for medical purposes. An article from the
Seattle Times some two weeks ago (
http://seattletimes.nwsource.com/html/nationworld/2010020934_potgrowers08.html) cites the White House Office of National Drug Control Policy as stating that, in 2006, the Mexican cartels derived 60% of their revenue--$8.6 billion of $13.8 billion--from sales of marijuana in the U.S. Most of this is grown in Mexico, but we've all heard the stories of cannabis-growing operations on public lands (National Parks, National Forests, BLM-managed lands) in the south-west, and those are cartel operations as well. In fact, the aforementioned
Seattle Times article is about how "mom 'n' pop" growers in "medical marijuana" states are now the biggest competitor to the Mexican cartels, and the biggest threat to their profits. Anything that causes less money to flow into the cartels' pockets is a
good thing.
Now here's another little factoid: home invasions occur disproportionately in residences which the perpetrators believe to house drug-dealing operations. Such homes are thought to contain large amounts of drugs, money, or a combination of the two, and if the robbers can't get cash, they can take the drugs and sell them for cash. But we also know that your average robber isn't the most intelligent person around (or they'd be doing something with a higher profit-to-risk ratio), so it's not unreasonable to suspect that if word gets around that you're growing marijuana in your house, even if it's a small amount for personal use or maybe to occasionally share with friends, some moron is going to think you're running a dealership out of your house, and will get some equally moronic buddies together to try to rob you. I can't fault anyone in that position for arming themselves against that eventuality, even if it is technically illegal (given that ATF form 4473 asks whether you're an illicit user of marijuana).
And it's not like there's a lot of documented instances of crazed dope fiends running amok with firearms; that idea's just
Reefer Madness-style voodoo pharmacology. Booze and guns are a much scarier combination, given that alcohol can exacerbate aggressiveness (which is a major factor in Britain's violent crime problem).