Hmm. I wonder if that would be possible to do without risking lawsuits. Wouldn't depression fall under a medical condition?

It does, but if you identify it before it can be reported, don't leave a paper trail, and find another reason (because there's always a reason if you want there to be one), you can probably get around that. I'm not suggesting that it would be ethical or even a good idea, but it's certainly possible that an early-detection system could be used to be very evil indeed.

You probably are generalizing that all countries in the world have great legal systems.

yes, I can't wait for the first company that fires people who "tended to engage in very high e-mail usage.". Although high p2p usage at work may be a reasonable excuse for firing :)