Unfortunately, you can't necessarily just say "no." As nice as it would be to turn away all of those new Android devices, BlackBerrys, and Hewlett-Packard and Lenovo tablets, you're not going to be able to keep them all out. But at least you can be selective as to which devices you allow, which you put through some sort of acceptance testing and which you just flat out reject.
Let's start with Android devices given the fact that a very large majority of the new smartphones and tablets will be running some version of the Android operating system. Most of the time, this is very good news because Android, in its current incarnation, is very stable, reasonably secure and highly flexible. You can create business-specific apps for the devices, and you can use these devices with virtually every carrier on the face of the Earth.
The problem is that the Android world is fragmenting. Each manufacturer and each carrier presents Android in a slightly different manner. Most of the time these are simply extra-value apps that give you access to unique carrier services. Sometimes these are apps or attributes implemented by whomever made the hardware and installed Android. And sometimes these are limitations that remove features that other similar Android devices might have.
The problem is when the smartphone or tablet needs to support a specific function, such as tethering for example, and the device doesn't support it. A more serious problem is when the device ships with an older version of Android that has no clear upgrade path or doesn't have access to the Android market. While the vast majority of Android devices don't suffer from these problems, some do. Some of the really low-cost devices ship with early versions of Android that can't be upgraded, for example. Some also ship without access to the Android market, meaning that access to anti-malware protection is eliminated.
For the tech staff, this means that you're going to have to evaluate each new device to see if it can be allowed into the enterprise. You may need to place limits on acceptable devices (for example, requiring that Android devices must be running version 2.2 or better to be allowed in).
I focus on Android devices here only because of the sheer number of new devices anticipated at CES, but the same issue applies to other devices. Will it matter if your BlackBerry users show up with version 5 or 6 of the device software? Will the BlackBerry Desktop Manager v. 6 cause problems? Will HP's WebOS work with your existing environment whenever it ships? The fact that it worked fine when it was from Palm doesn't necessarily translate to operation after HP updates it.
The only thing you can really do is put into place a set of requirements and a set of procedures for handling requests, and then stand back and wait for the flood that's sure to come. Good luck.