I used to teach classes taught over tv or online. For my work, I just needed a way of communicating with the students. You can begin teaching with a test to see what the student knows in case, one way or another, the set of required learnings has already been mastered. A test at the beginning is often called a "pretest". Using one can be a good idea but it can be alienating for a student to face question after question that can't be answered.
Once we had some time for listening or reading new material presented on tv or websites or in a paper textbook, it was time to test for learning. Email was very good for that purpose. But, I realized that I could have taught by exchanges through fax machines. We could have exchanged information by carrier pigeon or through village drums or over telegraph wires. There were multiple ways to communicate, multiple methods or channels.
I wondered if there were people who had a good fax machine or a handy coop of pigeons who wanted to learn with me. Maybe it would be easier, cheaper, faster, smoother or deeper learning if they could use a more familiar way to learn. That issue was on my mind twenty years ago but similar ones are emerging today. I have now run into two different companies that have multiple web sites that work differently and evidently somewhat independently. I get the feeling that I could sign into one and perform certain communications and account manipulations without the other sites of that company knowing what I did or crediting me. One of the businesses has a new way of sorting those that need to go to the right from those that will be handled on the left. Just as the bank can take half a day or more to update all accounts, other activity can take time to register. Meanwhile, if I read the "wrong" page and see outdated information, it can confuse me.
I try to stay alert for instances of multiplicity. There is a movie by that name in which Michael Keaton is cloned or something and suddenly he and the world are faced with multiple, duplicate versions of himself. Duplicate but independent. If there are several versions of you wandering around, doing things you might not want done with people you don't know or like, it could be troublesome. Similarly, if we say customers with a last name beginning with A to M should conduct business here while others should connect there, we may shorten the initial line for service but we will get certain problems.
In some ways, both nature and modern life are about multiplicity. If a guy makes money selling rags, I may get in the rag-selling business. Whatever succeeds might be copied. Probably will be eventually and maybe more than once. With multiple ways to notify people, we get problems. The opening of "The Hitchhiker's Guide to the Galaxy" tells the story of a local government unit notifying citizens that a highway is going to be built right through your house and the notice warning you and giving you time to protest has been on the village bulletin board for months! It is not our fault if you don't keep up. But the more bulletin boards, summonses, warrants, emergency phone calls, voice mail messages, texts, etc., etc, the more likely you got trouble.