From the site "NetLingo" (
http://www.netlingo.com/word/scrobble.php)
Scrobble:
a.k.a. scrobbling Part of the appeal of Web 2.0 is to find other people who share similar interests, herin lies the meaning of "scrobbling." To "scrobble" a song means that when you listen to it, the name of the song is sent to a Web site (for example, Last.fm) and added to your music profile. Here's how it works: Once you've signed up and downloaded Last.fm, you can scrobble songs you listen to on your computer or iPod automatically. As a social network, once you start scrobbling yourself, you can see what artists you really listen to the most, view your listening habits on your profile page, and allow others to see your tastes in music. Companies (such as Last.fm) use this data to organize and recommend music to people, to create personalized radio stations, and to see what other users listened to the most.
Confused no more!