Earlier quoted context omitted.
I worked for the Department of Homeland security as a contractor in 2009 to develop software for exactly such a use case. The operation for such merchandise is to ship products to basically an arbitrary address (sometimes knowing that the actual resident is on vacation, I suppose), and then have someone on the delivery end intercept the package. In these cases, the only realistic option for officials is to intercept…
I'm not saying it doesn't happen. I'm saying that the risk-reward ratio is way too skewed for me to give it a second thought.
So yes, it's possible that drugs have been mailed to you without you knowing it. In rare circumstances (especially if you just moved into that address, for example), you might be arrested to figure out what's going on. But it becomes hyperbole to suggest that you will automatically be charged and put in jail because of a random drop shipment (though I'm sure some HN person will find a counterexample just for the sake of doing so).