ray_afraid said:

Obi-Wan supposedly screaming like a dragon makes NO sense.. Surely the Tuskens know what the beast is supposed to look like and surely they can tell the difference between a large dragon and an old man in a hooded robe waving his arms around. I mean, they all turn and SEE HIM COMING! They run because they know who he is and what he is capable of. That's why "they'll soon be back and in greater numbers."

Their fear of Obi-Wan is more interesting from a storytelling perspective, as well. He's lived in the wastelands for twenty years at that point. They probably had a few encounters where Obi-Wan owned house.