Why do pedestrians walk down the middle of the road?

Around here, there's a residential area where a lot of people walk/jog in the morning. This morning I was cutting through there. There were three joggers heading toward me: One near each gutter, and one right out in the middle. Figuring he would defer to (his) left (i.e., on the edge of the road facing traffic), I moved to the left. Instead he started drifting right, tracking me, then just as I was on him, he put his right arm out, almost hitting me. He calls out "Car up!" (A car was coming up behind me.) I'm not sure what the hell he was thinking. I almost stopped to ask him, but figured his logic would be so out of whack that it wouldn't be worth it.