In teaching industry analysis, I always make a point of discussing network effects as a potential barrier to entry (see Peter Klein’s comment to this post on the term “network externalities”). Usually, I use an example like the iPhone FaceTime application which increases in value depending on the number of family and friends who have iPhones. This, in turn makes it hard for rivals to enter because of the need for a large installed base. Google+ is another example in it’s failure to make much of a dent in Facebook’s market. Now, a new app gives discount points to students for locking their phones based on the number of other locked phones in the same vicinity. As such, when the whole class locks down using the PocketPoints app, they all get discount points. This pushes everyone to adopt the same app to get the most points and makes it hard for a competitor to enter. This might also be a nice way to turn the class into a lab to study game theory, or incentives. It does all this and keeps people off their phones in class! The following video describes the app.
Heard Through Virginia Postrel