lupi,
I dunno, I think it might matter. If you subscribe to the "multi-hit" theory of cancer, every hit counts. You're right in that we can't control for all the background radiation that we are exposed to, but judging by how much time all of us here spend in front of the computer checking Anandtech for hot deals, over a lifetime, that's a lot of radiation. At least, that's how we might justify the purchase of that new LCD with our wives/girlfriends.