That you need to know fewer people is significant, and even more so is that you not meet in person that is why the "Dead Drop", "Dead Letter Box", etc is such

That you need to know fewer people is significant, and even more so is that you not meet in person that is why the "Dead Drop", "Dead Letter Box", etc is such a common tactic in espionage. deadSwap is a file sharing system/ urban game based on the concept. When done correctly it is very effective and very difficult to sting, thus it has been a standard in spycraft for decades.