At a high enough dose, sure. But study after study over the last decade has shown coffee to have a positive effect on everything from diabetes to Alzheimers.
Not for me. Coffee, anything caffeinated actually, makes me sick like I have the flu. The older I get, the more sensitive I become. I can't even eat chocolate anymore because of the caffeine content.
Also, I don't think most people drink more than 2 cups of coffee per day -- if I know someone who drinks more than 2 or 3 I'd think they have a problem.
I'm not a medical professional, but my understanding is that at least for the anti Alzheimer effect, it is due to the caffeine, specifically the effect it has on dilating capillaries in the brain.