The question is, why did they need an informal communication channel? What made this easy, and why was using a correct channel considered too difficult? Maybe Edward Tufte will write about this someday, as this might be another example where user interface design ended up having a big impact on world history (Tufte has written about John Snow using a clever map to end the cholera epidemic in London in 1853 and the Challenger shuttle disaster of 1986, the launch being allowed partly because the engineers from Thiokol were not able to present their information in a comprehensible way).

The article says:

"But the rest of the agency had become too reliant on the system, which was originally intended to only be a temporary communications channel, and had left the relatively insecure site up far longer than intended and used it to send information that should have been reserved for more secure channels. "It was never meant to be used long term for people to talk to sources," the report quotes one official as saying."

So why did it last so long? What did it offer that the more official channels did not? What kept the agency from developing technology that might have allowed better protected communication channels that might have also been easy to use?

Protected communication is not a sideline for the CIA, it is the core competency. This is something the CIA is supposed to be good at.