What is Digg?
Digg is a user driven social content website. Everything on digg is submitted by the digg user community, and after that other digg users read submissions and digg what they like best. When a story receives enough diggs, it is promoted to the front page for the millions of digg visitors to see.
The obvious effect on a website after a front page digg article is the huge increase in visitors and traffic. All those digg readers can saturate the site completely, causing the site to buckle under the strain. The Digg Effect is the term given to this phenomenon.