I know what you mean - I have the same problem. For me, it's worst with television: I can't have a conversation with someone if there's a TV on in the same room. I'm not sure if this is the opposite to the flashlight simile, or just an example of an inability to direct it at will.
Well, television (particularly ad-supported television) is actively trying over and over to grab your attention, so it's not terribly surprising. I have a hard time focusing when there's a tv in line-of-sight, too, and it gets worse when I haven't watched broadcast tv for a while.
I remember hearing somebody (Douglas Rushkoff, I think) suggest that ADD-like behaviors might be an adaptation to a childhood in which one is inundated with aggressive, flashy advertising. Adapting to reflexively ignoring things that are designed to steal your focus probably affects your brain in the long term, much like meditating regularly can.
Interestingly, I find that this tends to affect the men of my family more than the women. My mom, sister, and wife don't seem to have this problem at all. While both my dad and brother all suffer from an inability to hold a conversation if the TV is on.
