Twitter is a powerful tool for known and popular people, for less known or even unknown people is just another useless way of expressing your thoughts into the universe 'cause from what it looks the universe is the only big thing that listens to you, through Twitter or Facebook, either way.
As in the case of a blog and its readers, to have a lot of followers you need to be a public person, with a lot of fake friends, and who does participate to a lot of public events of an economical, social or political nature. To have people express their interest towards your blogger, twitter or facebook products you need to express an interest too, true or fake, 'cause sometimes it may be difficult to read stuff from hundreds of people. Except when you are a guru of some kind and people will follow you blindly in hope for free wisdom if that's the case.
Twitter is another way to notice how shallow some people are, they start following you, and the minute they see you don't follow them back they unfollow in a blink of an eye, some people expect it to be mutual. Well, from where I stand Twitter is one thing that should not be mutual, 'cause for me Twitter is like the favorite newspaper I never had, when I visit my Twitter account I wanna read interesting stuff, make a reply of some kind and if it is the case to socialize a bit.
Not every single person I follow follows me back and don't expect them too, if they find me interesting and worth of following back kudos to them.
As I said, there are individuals who start following me and expect to do the same thing, but if I see that we have nothing in common I'm sorry but I'm not going to follow back. I just don't want to have other pretty much interesting tweets buried in the load of crappy ones.