etailology

While this article (excerpt below) provides considerable value on its own…

The widgets are designed to engage users for longer periods of time on the Facebook website by creating activities for people with similar interests. Essentially, Facebook’s profiles have changed from a place where you just read about someone to a place where people can engage in activities. This change is effective in generating traffic for Facebook, as well as for the companies creating user apps, and has been termed the Facebook Effect.

Not to be overlooked is the Quantcast page it links to, which details the “Facebook Effect.” Another excerpt:

The Quantcast charts below (figures 1 and 2) reveal the relative growth in daily uniques to three leading widget publishers, each with multiple applications running on the Facebook platform. Since Facebook’s open platform initiative began on May 25th of this year:

• Slide, the leading personal media network, has more than tripled its global reach in Web site traffic.
  • Slide grew domestic U.S. daily unique visitors from approximately 312,000 to more than 1.1 million, an increase of 265 percent.
  • Slide grew global daily unique visitors from approximately 753,000 to more than 2.3 million, an increase of 207 percent.