I do not see how Twitter is a truly necessary for anything other than distributing a shortened version of a mass text message. I got my own Twitter account just to see what it was like and I found it to be pretty close to pointless. You have 140 characters to tell the world anything you want whether it be how boring your homework is to what your plans are for the next hour of your life. I can do that exact same thing on Facebook, except there's no 140 character limit on my status. You can also have a small bio on your Twitter profile, up to 160 characters, so basically you have a text message to tell someone about yourself. If you can write a personal bio of yourself with less than 160 characters or one standard text message, you need to pick up some new hobbies there sport. On Twitter you can change the background of your Twitter page and such but that's about it when it comes to personalization outside of your 160 character bio, picture, where you are, and a link to another website of yours (maybe Facebook if you so desire). This may be the only useful thing about Twitter, it allows you to attach another website to your profile, like I did with my Facebook page, so you don't have to have such an elaborate profile on Twitter. However, what's the point of having a website with a short bio to point you to another website with a bio on it?
I don't see much point in Twitter because everything I can do on Twitter, I can do on Facebook better. I can have a better bio, more room to write statuses to announce to the world and so on. Twitter basically has just taken the status bar from Facebook, liquidated it and made it into a website. I see no use for this at all other than just having another way to shout out to the world on sentence at a time.