Chat is very useful as a work-related tool, for discussing things with colleagues in another room without disturbing other colleagues in the same room.
However, as I am only online at work and very occasionally in the evenings to do specific tasks, I do not want to use it to spend time chatting to people at any great length. By all means send me an email or a facebook message, which I can respond to if I have time, and at whatever length I choose, but chat is invasive, and this is why I only use it for work-related purposes.
There so many blogs and websites I ought to be reading, friends to keep up with, emails and all that - it's difficult to keep up. Of the blogs I visit, I probably only read 10% of their output - and there are so many more that I would like to read, but don't have time. And at the moment I am doing research for my essay, which is overdue, and needs drastically restructuring.