Not all companies are as paranoid as others. While maybe not in your case, a lot of large companies are very concerned with leakage of sensitive information and do not look favoritly on using external storage for documents, calendars and others. Those same companies would also prohibit use of web mail services as to minimize the ability of its employees to bring into the company malware. Depending on the line of business you are in, there are laws that require that all communications from an employee be recorded, which can not happen if you use a web mail service, POP or iMAP service that does not go thru the exchange server.

There are all sorts of sizes of companies and each have different levels of paranoia. A lot of what is being implemented in the iPhone goes along the lines of the security capabilities of the Blackberry and it is designed to serve the majority of the paranoid companies.

At the MOST paranoid companies:
Apple has yet to release all the details, but expect that companies will issue the iPhone, they will pay for the AT&T service and they will lock the phones so that only those applications they deem safe can b e installed and installed only from an internal and designated server. Expect all the data also to be encrypted and only allow email from the exchange server. Also expect that all iPhones will be required to have a password and that the device will be automatically erased in the event that someone enters the password incorrectly N number of times. For those companies ....... Google Apps would be considered dangerous.

Your company may not care about the same issues and may allow you to use personal devices and as many email sources as you like.

We are not all covered by the same rules and regulations.