The more I think about it the more it seems like a good idea, I know people who update their facebook status several times a day (usually saying they are bored, depressed, asking questions, or making some vaguely amusing gag about something they've seen on tv) and can't help but feel that they'd be better suited to Twitter. One of my more geeky friends obviously uses Twitter in some group with work-related people as he's got it linked into his FB which constantly gets updated with random techie questions which nobody else would give two hoots about.
The worrying thing is it is slightly contagious and I've started setting 'amusing' FB status' sometimes. Bleh.
In some ways, it's the modern day equivalent of /away or nick|BLABLA on IRC. You know, some kind of way of saying what you're doing, sometimes to try and promote how super cool you are. I even used to have a /bed alias to change my nick to BedTime, tehehehe!