In the early days of E-mail, people created “auto-responder” programs like the Unix vacation utility, which would respond to incoming E-mail with a reply like “I’m out of the office until Monday. Take a dump and reboot.” Of course, it wasn’t long before two people running such programs accidentally got them talking to one another, causing great hilarity except to the users whose disc partitions filled up with thousands of copies of inane messages. Most such programs now take care not to get into loops, but it still happens.
Even more fun is when mindless bots start talking to one another in the real world. How did a copy of Peter Lawrence’s book about Drosophila, The Making of a Fly, end up listed on Amazon for US$ 23,698,655.93 (plus shipping)? And what caused the US$ trillion U.S. stock market “flash crash” of 2010-05-06?