Mr. Milestone
Mr. Milestone is a part of the Twitter Tag Project. Mr. Milestone will send a tweet when you have reached 100 followers. It will repeat every 100th follower so you’ll know how popular you are!

Traffic rankings are sourced from multiple sources, if available, for the Twitter application. This includes Alexa, and Compete rankings.
January 12th, 2009 at 2:14 AM
This can certainly be a very handy application, but in my opinion, people need to focus on quality and not quantity on Twitter. This seems to be an application which has an underlying purpose of getting people to focus on quantity.
Cheers,
January 12th, 2009 at 7:17 AM
To be exact, quantity would be counting the number of twitter updates. But quality is focus on how many followers and influences you have. This app counts the number of followers.