Twittered links are clicked. With about 1,000+ followers, my last five Tweets with links averaged 30 clicks, about 3% of total follower base. However, assume 20% are online at the time of the Tweet delivery (I’m guessing, this ClickZ study says in 2005 blog readers were online 23 hours per week, about 14%). Then, the actual clickthrough rate approaches ~ 15%, all within a window of minutes. This points to Twitter as a high affinity / high trust networking tool that spreads news and ideas quickly from individual to group to group.
Twitter app Tweetburner measures these clicks; I learned this at BlogWorld’s Twitter panel.