Dave,

without having read the article, my first question would have to be "was the question based on social or business e-mails sent?"

E-mail is still an important method of communication for businesses of all sizes, even if it is only to confirm a telephone conversation or send documents to a company. I certainly wouldn't want to send private T's & C's via a social network chat facitlity, and wouldn't see a social networking site as a place to conduct business - but maybe to attract some.

If text messaging and IM is to take over e-mails as a form of business communication, I think it will still take some years to overtake e-mailing.