Mine was named Mac's keyboard too LOL Maybe that's the standard for all?
Found how to rename it in the manual 09 wireless keyboard. You gotta be on a Mac.
Apple>>Sys Prefer> BT and click on Action pop up and choose rename.
The only Mac I have dual boots Win7 and I hadn't been in OS-X for about a year. After I updated Snow Leopard, the "rename" tab came up and I was able to change the name.
I'm guessing "mac" is the Geek Squader whose job it is to check returned keyboards.
Stop me, before I shop again.....