Hiya-
I'm pretty sure attaching two USB keyboards won't hurt your box. The worst that could happen is one might not work.
However, as far as hooking up two Optimus keyboards, it's worth noting that according to the
Optimus website, the drivers for the current Optimus mini three keyboard do not support more than one attached at a time, "as of now". That's the bad news.
(I'm assuming that the drivers for the full keyboard will be the same way, at least initially).
The good news: According to the same FAQ: "Optimus Configurator automatically recognizes the application and uploads images and commands for the current context." That appears to mean that the drivers can be set up to be application-specific, so their functions (and presumably the images displayed on the keys) automagically change depending on the currently running app. Is that (sorta) what you were looking for when you said you want multiple keyboards to "have multiple keys set for different tasks"?
My Macally keyboard and MS mouse do the app-specific thing. Works great. My Logitech drivers do not have application-specific settings, so I rarely use the MX700 I bought a year ago. It's relegated to my rarely used old-computer-turned-file-mule box.
Anyway, I would suppose that if they sell a metric buttload of these keyboards (and if it's priced right, they will), eventually the drivers would support more than one keyboard and all kinds of other goodies. Eventually we might see an Optimus with a RAM cache to hold images and animations? The drivers will be open source, and I'm pretty sure there are a few folks with a few ideas for a keyboard like the Optimus. So you could have, say, a big flag waving behind the keys showing what localization was currently active, programs for teaching how to type, system monitoring apps, or (dare I say it) ads on your keys [shudder]. Alls I know is I want one yesterday.
Drewstre