Operational Security can be a tricky thing. A solid way for a criminal enterprise to undermine it would probably choosing a courier service with a law enforcement arm with a rather lulzy history of alignment against things that entertain. Until some sort of Star Trek like replication system becomes available and sending physical goods with proper GPG envelopes becomes possible, it may be right to consider the United States postal service the wrong counterparty to trust to deliver drugs to your home. Let us consider why this is likely the case.
From the Smoking gun today we have news that one of the biggest Narcotics dealers on the Silk Road was busted and turned information in July. It seems the Postal Insectors had been busting and turning people informant for quite some time. Now a lot of lessons that should have been learned from the Silk Road fail pile involved technological lessons where going to revelations from the Snowden leaks could help provide illumination. For this though we don't need to go as far as Snowden.
No matter how you perceive the operations of the Post Office or any other courier service, it is not some magic black box that move your package from A to B. That to you it appears to be one, doesn't make it a magic conduit that moves packages. It is a complex machine, a complex machine that seems to have transformed over the years to detect things like anthrax and ricin in transit as it has become even more opaque to outsiders. It be worth assuming that if there is equipment to detect a complex protein like ricin in the postal back box, that much cheaper equipment for detecting certain small molecular weight organic compounds1 exists somewhere along the system. Then once a package is identified they bring in the drug dog, because it is a more palatable explanation and serves to vindicate the continued use of drug dogs in spite of their ineffectiveness.2
That you "don't know", "can't know for sure", or "don't think they'd do something like that" and consequently don't plan for it means you are kind of unfit for the contraband business as either a business man or as a consumer. If you think that being otherwise respectable, or pale, or boring might save you from getting roped into a law enforcement investigation as a small consumer think again. Those are the same traits that would make you more desirable to turn informant, as former NFL advertising operations manager Michael Shapiro has probably been pressured to do, though the release of his name suggests he likely has been resisting.
Anyway Silk Road refugees, it is probably best to take your drug buying back to the highway toilets where it belongs.
like cocaine ↩
Here's a decent introduction to that problem: http://www.ombo.nsw.gov.au/news-and-publications/publications/reports/legislative-reviews/review-of-the-police-powers-drug-detection-dogs-act-2001 ↩