>>I use night vision goggles as part of my job all the time. I use some of the most expesive ones made.
I do too.
I can tell you that unless you were standing in front of a very light colored rock cut staring at it looking for shapes, NVG's wouldn't work that good.
That's the question I had. Basically the concept of NVGs is to take light at the IR/Near-IR end of the visible spectrum and amplify it. While this implies that you're looking at a "heat-sensitive" view of the environment, the NVGs are also showing you the difference in albedo (basically the reflectivity of an object) between objects of interest, which is why you get high contrast between an asphalt road and a plowed field.
Since snakes don't generate appreciable heat, there won't be too much difference in the heat signature of the snake and a rock face behind it, but if snakes had a measurable difference in albedo of their skin vs. albedo of their habitat, you would be able to spot them more easily. I haven't tried using NVGs to find snakes so I can't say for sure, and I don't have any captives to use to experiment.
Even the most exspensive bino nvg's give very bad depth of field
That's true. You don't look "through" NVGs as you do with optical binoculars; you look "at" NVGs since you're basically looking at two TV screens (light enters and excites the phosphor plate which produces the end-result, two-dimensional image).
trying to drive with them.
My friend got pulled over driving with NVGs on (no headlights). 
I've thought about the idea too but decided pretty quickly that it wouldn't work (with current technology anyway).
They're still fun for chasing the wife around a darkened house!
Anyway, rather than just go on hunches, it would be fun to set up a controlled-condition test to see if THEORETICALLY you could use NVGs as an aid to finding snakes. I think PRACTICALLY speaking, they wouldn't help out enough to make it worth the effort/cost because you'd be scanning a range of surfaces, all with varying albedo.
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Chris McMartin
www.mcmartinville.com
I'm Not a Herpetologist, but I Play One on the Internet