Well as much as we hear that there is no issues for those who own Apples there is and it was demonstrated at Blackhat (Defcon 17) this year.

Apple keyboard firmware hack demonstrated

APPLE KEYBOARDS ARE vulnerable to a hack that puts keyloggers and malware directly into the keyboard. This could be a serious problem, and now that the presentation and code is out there, the bad guys will surely be exploiting it.

The vulnerability was discovered by K. Chen, and he gave a talk on it at Blackhat this year. The concept is simple, a modern Apple keyboard has about 8K of flash memory, and 256 bytes of working ram. For the intelligent, this is more than enough space to have a field day.

K. Chen demonstrated the hack to S|A at Defcon today and it worked quite well. You start out by running GDB, and set a breakpoint in Apple's HIDFirmwareUpdaterTool. This tool is meant to update the firmware in human interface devices, hence the name. The tool is run, a breakpoint set, and then you simply cut and paste the new code into the firmware image in memory. That's it.

Here is a mini video of K. Chen showing how it works
 

now in the story they mention a PDF that shows the code

You can read the code PDF HERE

So why didn't they just tell Apple about this?

Apple Keyboards Vulnerable to Firmware Hack

They would've told Apple about this, but the last few times when they called Apple in similar cases, the company didn't even return their calls. "Don't believe them when they try to spin this as minor, owning a keyboard gives you ownership of a system."

Chen can write a tool to lock down the firmware, he says, but he's waiting for a possible official solution from Apple before he attempts to do so. However, he is afraid that Apple will fix this in current and future versions of Mac OS X only, leaving the keyboards open to be attacked from other sources. The fix needs to be implemented at the hardware/firmware level, he says.