I see the article you listed Rick states this " They can surprise you," . I happened on to one this Monday that was in a place I was not expecting. I put three pics from that encounter at:
http://www.flickr.com/photos/35054303@N00/?saved=1 , or click on the Wizard's picture link below to see them too.
Here is the closest photo of it: http://www.flickr.com/photos/hotspringswizard/7548499776/sizes/l/in/photostream/
It was a South Western Speckled Rattlesnake and it took me a bit to recognize just what it was since from the distance I was at all I could really see was its head on top of a smooth rock I had placed at that location ( see other two photos of it ). I checked it out from about six feet a way and it never rattled the whole time. I was on top of a peak at an elevation of 5,000 feet.
On some recent hikes to Deep Creek I have come across what I think were the species of rattler called Southern Pacific. They were very big, maybe 5 feet and dark colored, almost blackish. One of these did not rattle either as I passed it by and another only rattled when my dog got within about four feet of it. As you can see from the photos of the South Western Speckled Rattlesnake, they can be in very tight cracks so you really need to be very gaurded about any small recesses where a snake may be laying. I see the speckled rattlers often out where I hike in the desert mountains around our home.