When a website ends up denied (saturated with external
communications requests, such that it cannot respond to
legitimate traffic, or responds so slowly as to be rendered effectively unavailable) due to a sudden enormous spike in
popularity.
A
Social Network Denial-of-Service (SNDoS) could be started by one
Facebook user setting his/her wall status to: "Go to
urbandictionary.com, type in your first name, copy and paste this as your status and the First entry for your name under comments"