Social Engineering and Koobface virus

Koobface, whose name is an anagram of the word "Facebook", is a special worm that spreads through messages in social networking sites like Facebook and myspace. One of the ways it affects users is:

1. One of friends writes a message on your wall with a video link saying "Funniest video ever!" or "My Home Film;)"

2. When you click on the link, it asks you to install the "Adobe flash player" to see the video.

 which is actually the Koobface worm.

3. You download it and become a zombie.

More on KoobFace:
The Real Face of KOOBFACE, analysis by Trend Micro.
Koobface virus hits facebook
Koobface scam by Berkeley researchers
Wiki has some good links