I am presuming you had a good zoom lens on your camera because who would be silly to lay on the ground in front of one of them.
They're not quite the demons everyone makes them out to be. If you've ever been to a picnic ground that has foraging lace monitors, these guys are similarly behaved - just many times larger! You wouldn't want to do something suddenly, like trip and fall over in front of one, but otherwise for the most part they are just mildly curious. As one goes further away from the ranger stations the dragons often become warier and are more frightened and annoyed than anything else. At first, when seen from a distance, they duck their head down (as a lace monitor would) in the hopes they haven't been seen, but when you get close they puff up their throat and slowly walk away or, in some instances, hold their ground and try to tail-whip if you get too close. Some just look bored by yet more tourists wanting to take their photo. The scariest moment we had was when one of my mates accidentally dropped his backpack while we were photographing a couple of huge males outside the ranger station on Komodo. One of the dragons raced over at surprising speed, thinking it was food. My mates and I muttered "nobody move a muscle" and waited until the dragon calmed down out of 'food brain' mode.
The small ones look a lot like their closest relatives, lace monitors:
The big ones are unmistakeable!
Here's one of the males near the ranger station on Komodo coming over to check me out. A few seconds after I snapped this the ranger advised me to step back.
I put together a video - I was silly enough to use copyrighted music, so it's been removed by youtube

. Unfortunately, the editing only makes sense when the music track is included.
[video=youtube;z85V2k4TWDs]http://www.youtube.com/watch?v=z85V2k4TWDs[/video]
At 3:06 there's a short clip of a dragon approaching me out of curiosity - in the unedited clip it got close enough that the video was mostly scales walking past, but the ranger quietly held his stick out below the camera to let the dragon know the limit of how close it could get. I was very impressed that he didn't walk out in front of the lens to do this and the stick didn't show up on camera.