However, even with all of this you will likely have to figure out how to support this in some way before the end of the year.
Web Access Only
There is likely no more risk to this device than there is to a borrowed PC or Web terminal in a common area, and it is relatively unlikely the iPhone will be running a key logger (a service that captures IDs and passwords often found on unsecure PCs and terminals). Outlook Web Access isnt bad, assuming it works on the iPhone, and it is better than nothing. Watch the forums after launch as I expect a lot of folks will be trying to get this to work.
This means there may actually be a benefit to using this phone, which is in the users control, over a piece of equipment that is not. Given you cant really prevent it anyway, recommending and assuring web access may be a better path than saying no and having folks try it anyway.
Sometimes all the employee or executive wants is someone to try to help them and, if you can warn them about what doesnt work, while helping them find what does, youll likely have a supporter at the end of this process and IT can use all the support it can get.
Big Changes Ahead
Lets step back and take a look at the Macro picture. Apple is driving a massive change into the cell phone segment. If you couple this with efforts like the Palm Folio, UMPC, and Blade PC you should be seeing huge red flags indicating a massive approaching change in everything from PCs to Cell phones and from related software to services. This change isnt just in the enterprise either but is likely to hit solidly in small business and consumer. Companies driving this change are Apple, HP, Cisco, Palm, RIM, and even Microsoft (and this is just the short list).
We are on the forefront of a massive change; unfortunately we cant hide from it, because even if we could prevent our executives and employees from moving, our partners and customers likely wont ask our permission. This change is broader than the iPhone alone; Microsoft is working with Apple and a number of Linux distributors and improving dramatically interoperability between a variety of platforms. If you wanted choice, you are probably going to see one hell of a lot of it shortly.
It is probably time we started looking aggressively at some of the emerging technologies and put in place strategies to improve our own Agility because we likely will be dancing fast in the next few years. So learning a few steps now could keep us from falling on our butts.