  How does a new startup drive the popularity of competing websites into
oblivion like Facebook famously did to MySpace? This question is of great
interest to academics, technologists, and financial investors alike. In this
work we exploit the singular way in which Facebook wiped out the popularity of
MySpace, Hi5, Friendster, and Multiply to guide the design of a new popularity
competition model. Our model provides new insights into what Nobel Laureate
Herbert A. Simon called the "marketplace of attention," which we recast as the
attention-activity marketplace. Our model design is further substantiated by
user-level activity of 250,000 MySpace users obtained between 2004 and 2009.
The resulting model not only accurately fits the observed Daily Active Users
(DAU) of Facebook and its competitors but also predicts their fate four years
into the future.
