Visible crew/equipment: Mike boom shadow can be seen on the lower left portion of the screen when Steve Martin is talking to his "father" outside the barn. (00:08:50)
Visible crew/equipment: Carnival biker chick goes through a flaming hoop and falls down after going though it. Just before she goes, you can see a rope tied to her to pull her off the bike after she passes through the flames. (00:33:30)
Visible crew/equipment: In the gas station scene, when Navin returns with the tires for the Latinos, a crew member becomes visible in the office window where he just came from. The crew member jumps into view and seemingly realizes it and hides.
Answer: Navin self-applies the "Jerk" epithet early in the film, using it not in the sense of someone obnoxious or mean (as it is used in most cases), but in the sense of a stupid person. He's saying he blames himself and his lack of intelligence (though, as you say, it is usually simple naïveté) for ending up where he is (broke, homeless).