It is a known fact that iPhone has not penetrated in the corporate sector yet. It might take a while for Apple's device to conquer the corporate sector, however there are many signs that large companies take iPhone into account.
At least, Bank of America, yes, the nation's one of the largest banks, has implemented a version of the site designed specially for iPhone. Interestingly, this was discovered purely by chance by Dan Moren, who desperately needed to find out the location of a nearest BoA ATM.
You can read the full story at: http://iphone.macworld.com/2008/01/boa_banks_on_an_iphonespecific.php