First, you can't just walk up to any computer with a USB port, plug in the iPhone and suck data. You have to install the application on every computer you want to copy data from, and install it on a destination computer. Secondly, you have to have the rights to connect writeable USB devices to that computer. Even basic experience with user privilege settings, GPOs, and MCX policies lets you prevent either of those from happening on either Windows or Mac OS X. Simply following best practices will keep users from installing random software, and hooking up random portable storage devices to the computers on your network. Anyone thinking this hasn't been something to deal with until the iPhone is at best ignorant of a string of problems involving far cheaper USB flash drives, or in deep denial.
As far as remote access to data via EDGE or wireless, I'll just say, Good luck with that. Right now, the only way to wirelessly get data on or off an iPhone is via e-mail. Considering most attachment size policies, you aren't getting a ton of data off your company's network via e-mail. But again, keeping random wireless devices from your network or your e-mail servers isn't rocket science; in fact, it's not even particularly tedious. If your network is properly configured, this is not a Godzilla-level problem.
One security issue that has been raised, and is legitimate, is the inability to remotely erase e-mail data from the iPhone. I know at my company, this is a requirement for us to allow you to get e-mail, etc., on your phone, and we're not alone. If you're using e-mail the way, well, everyone is, your company is probably sending sensitive info out on it, and a remote-erase feature for phones that connect to company e-mail servers is neither a minor, nor a luxury, item. If you have a need for that functionality, again, don't get an iPhone, and don't let them connect to your corporate e-mail systems.
If it sounds like I'm saying "Don't get an iPhone if it's not going to meet your needs," well, I am. While I'm more than pleased with mine, if I had to sync my personal cell with my Exchange server, and carrying two devices was far more onerous than it is, I'd not own one. It's not for everyone, and if you're in that group, don't get one. "Cool" doesn't override "not functional for your needs." Ever.
However, both remote management and Exchange/Domino connectivity bring me to my next point:
iPhone Application Development
This is one that has created a kerfuffle of Megatronian proportions, and while I know why, I'm still somewhat surprised at the vehemence. First, as I stated earlier, I have a solid bit of experience with both Windows Mobile and Palm smartphones. Both of those have essentially unlimited access for third-party developers, and while this is nice for those who want more toys/functionality, from a support POV, to be blunt, it stinks. Remember, at heart these devices aren't Internet terminals, nor PDAs -- they are phones. And yet, I've seen third-party applications, from both major (Quicken & AOL) and minor (Ilium Software) turn these phones into bricks. I watched a version of Pocket Quicken put a Treo into a never-ending soft-reboot loop. I've experienced how Ilium's NewsBreak can screw a Windows Mobile device straight into the ground to where only a soft reset will allow the silly thing to send or receive calls, because NewsBreak had locked up the radio so bad that you no longer had a phone. Talk about an "iBrick."
There are a few reasons for these kinds of problems, the biggest probably being the astoundingly small memory space you have on Windows Mobile and Palm devices for running applications and the OS. For example, my work phone is a Verizon XV-6700. It has a 128-Mbyte Flash ROM and 64-Mbytes of SDRAM. I don't have a SD card in it, but the only third-party application on it is GoodLink. So, for every single function on this device, from OS to application storage and run space to data storage, I have, out of the box, 172 Mbytes of possible storage. Of course, since most of that is ROM, I only have 64 Mbytes available for third-party application use or data storage.
With just GoodLink's e-mail and calendaring running, I have exactly 8.84 Mbytes of storage space and 22.52 Mbytes of program space available. Now, were I to add a SD card, I would gain a lot of storage space, but my OS and application execution space would pretty much stay the same. It's worse on the Palm side, since most of the time, all you can use memory cards for is picture and file storage. So all it takes is an application that's a tad careless with resource use, and your nice smartphone at best requires a reboot, at worst, a hard reset. It's not just smartphones -- I have friends with first-generation Razrs who swear at the AIM client, because it reboots their phone with astounding ease.