In my opinion, the only people who really need mobile e-mail are the staffs who do not work at an office: the road warrior, the sales rep. And then, I don't know if the hand held type is the best solution. But that's not for me to decide.
Where I work, lots of project managers run around from meeting to meeting with their Blackberry like gizmos which vibrate so much that meetings have turned into earth quakes. They do not respond to the e-mails right away (Swiss people tend to be polite in meetings) but more often than not, they read them.
None of these people are hart surgeons waiting for a transplant availability message or any other information of vital importance and 99% of messages could easily wait a couple hours if not a couple days.
E-Mail is THE killer app of the internet. It is the most useful thing on my computer and allows us to stay informed. The down side is that with everything else, too much of a good thing just turns it bad.
Some of us get an e-mail a minute or more. Not spam, just people who send out information and think we ought to be informed.
But the Gizmos are mostly for status display anyway and not really for information delivery; it's for status. Getting a Blackbery like device shows that you are important. It's a cost effective way for a company to make employees (male ones at least) happy. It certainly costs less than paying business class
We are flooded with information all day long and most of us do not have the mental or technical or organizational tools to deal with the amount of e-mails, or SMS and phone calls. Making it too easy to communicate can create a lack of communication because people don't know (and have no way of finding out quickly) what is relevant and what is not. I started to filter all the e-mails where I am alone in the "To" field from the others. I have started asking people to use key words and to post to mailing lists. Unfortunately for me, my authority is limited and I still get lots of e-mails. Thank God for the "Off" button.