I am going to twitter him? No - there's not enough space in 140 chars. Am i going to email him? No. He'll never read it. A few people may read it and it there is enough interest someone may point him to it (or directly through Twitter).
The point is that email is not right for a conversation. 25 messages to arrange a meeting where the overhead is 6 times the content CAN'T be right... and on a mobile (come on SMS has proven this in the UK alone).
A great point by Scoble is
"But when I left, my e-mail account was turned off. I don’t have access to that
.. and neither do THEY! Everyone loses.
Twitter, Jaiku and so on are not perfect - it gives people like me a chance to write something better. It's all a step in the right direction.
Email is dead as the primary communication method IMHO - i use it because, like letters, people still do things that way. But, for a few key emails, the rest is broadcast or spam. Communication is going to be about content and pointers to that content (tweets, jaiku's, others) - you write, suggest and maybe i read - kinda like reading an email subject line and deciding whether to read the email.
In saying that, anyone who thinks communication is going to be one dimensional probably thinks Google is the final answer in search.