Proximity I believe is only relevant in that a higher concentration of gamma rays will exist per a given volume the closer to the source you are. The way it works is that however much of an object will block out portion of the radiation. So say 95% blockage is what we're looking at for 8 inches of lead, this may be enough to avoid harmful exposure in some situations, but should you times the amount exposed to the lead by 20, then the 5% let in might quickly become unsafe.
There comes a point where no matter the amount of radiation, blockage is close enough to complete that exposure is next to irrelevant. And if that point is unrealistic for us right now, all that needs to happen is for new means to be developed.
It should also be noted that while Gamma doesn't have any mass, no EMR does. This means like, radio, microwave, x-ray, UV, IR, visible light and everything else on the EM spectrum, all "weigh" the same.. Or would that be weigh the same per energy? I dunno.. I doubt it matters since zero times .5 or 1.5 is still zero. Though I am still open to the possibility that EMR may in fact have weight after all and it's just small, like an electrons weight compared to a proton or neutron.
"George Bush says he speaks to god every day, and christians love him for it. If George Bush said he spoke to god through his hair dryer, they would think he was mad. I fail to see how the addition of a hair dryer makes it any more absurd."