Just been reading Dan Bobinski's column this very site - How multitasking and e-mail waste time - about how (apparently) research proves that the "human brain is not built for multi-tasking" and that "email should be rationed and scheduled for certain hours in the day" (paraphrasing) with a comment added to the column (from a vendor) even suggesting that instant messaging is a time-waster.
What a confused set of arguments.
We evolved to enable, and with the help of, communication. It brings us pleasure and allows us to develop further. We can hold together complex social groups because we can communicate with them.
Culture itself, civilisation, is only possible through communication. The human species has invested considerable evolutionary effort into gained the power of speech, followed by the ability to write, read, and print.
We know this instinctively and move towards new sources of community and communication. Telegraph, radio, television, fax, email, internet, mobile phones, and instant messaging all extend our ability to share feelings, information, and ideas. They extend the interrelationships that are possible bringing with them security (reaching out for a friend when lonely or afraid), escape from boredom (Mandella organised a secret system of note passing to overcome the three decades in jail), data (from who did what with whom to the best way of solving a problem), and organisation (how else can we schedule, align, and act?).
A company that thinks that it's people will be more effective by restricting their ability to communicate (even at the cost of momentary efficiency) will lose the bigger battle - the cultural war for smarter organisations.
Of course multi-tasking is a time-wasting, foolish and untlimately destructive approach to (dis)organization. You only ever have 100% of your attention available to you (often less than that). However you split it, each task in your 'multi-tasking' gets only a small proportion.
I've written about this here: Coyote Tries Multitasking Combating the Deadly Lure of Multitasking Nuts to Multitasking!
One of my better efforts was walking down the street at the same time as reading a report as the same time as giving editorial changes from the report over my mobile - whilst ensuring I did not get run over or knock anyone over at the same.