I actually just read that the telegraph has something to do with it. Because messages would often get cut off, the important content had to come first.
I agree. There is too much emphasis on marriage in our society. At this point in my life, I'd rather have great friends than an okay romantic relationship.
I prefer the simplicity of Twitter: I don't want pictures, I don't want video, I just want the info. (The only reason I'm on Facebook is because I am a college student and my peers are all on there.) I also feel that Twitter better facilitates useful information exchanges which is harder with the clutter of Facebook.
As far as the urban audience, I think one of things that makes Twitter a little closer to MySpace is that ability to customize your background. I think that might be a part of it, but certainly not all of it.