The Email Cascade
http://www.nethistory.info/History%20of%20the%20Internet/email.html
Emailing began as simply writing messages to people and saving them where the intended recipient could see it. In its early stages, messages could only be shared by users of the same computer. The earliest email system was called MAIBOX and was first used at MIT in 1965. The invention gained usage in 1974 when ARPANET began using it, adding hundreds of military personnel. As more and more people began using email, this created a cascade, and as of today, more than 600 million people use email across the globe.
This is closely related to the topic of cascades that we have discussed in class. The invention of email began as a very small network, but as more and more people were able to access it and began regularly using it, it gained more value to potential users, and eventually created an enormous cascade that has assimilated throughout the world.