I've actually had that happen lol... We were out on a training exercise on the moors at night and someone literally came within a few inches of stepping on my arm. It's incredible just how invisible you can be in normal camo, at nght if you are perfectly still.
This was right beside a fairly well-lit road, actually. It's hard to explain, but I remember not having to try very hard to be stealthy. This is somewhat counterbalanced by the fact that most of the time, as the spec ops guy, you're alone, enemies could otherwise see you far before you could see them, and the game had only one save per 30+ minute level.