www.ubervu.com is a great site to monitor conversations across multiple social networks (Digg, Facebook, FriendFeed, etc). The service also has a wonderful means of comparing topics, too. Consider the number of Apple iPad conversations and Tablet PC conversations.
Manufacturers should pay attention to these trends. There has been a considerable drop-off of conversations this week regarding the Apple iPad, however, the number of conversations still far outreached the Tablet PC (3310 v. 56).