I read the other day that some 'Tweeters' are buying followers (e.g. $100 for 5,000 followers.) Some are even creating phony Twitter accounts to fraudulently increase the number of followers they have.
While this may sound kind of silly, if you're trying to spread something, it makes a lot of sense as it will likely have the result of increasing your number of real followers; as we know, people like to follow people that other people are following, just because they're being followed.
I'm watching Twitter's progress pretty closely these days because I think it's so fascinating to watch this little startup evolve into what could be the most powerful communication tool ever conceived.