Nice comments Natalie. The response of social epidemiologists to GxE are somewhat mixed. One perspective on this idea that we can use evidence on GxE to identify people who are especially vulnerable to adverse environments is "why not just protect everyone from adverse environments?" For example, we found that education is especially protective for HbA1c levels among people with high genetic risk of diabetes. So, the "use GxE for screening" perspective would suggest we need to identify people with high genetic risk of diabetes and make sure they attend college. That seems absurd- everyone should have the opportunity to attend college. Same thing if we consider the environment something like maternal nurturing or safe childhoods... even if you have genetic resilience to have a good health outcome despite an adverse childhood environment, you should still not be exposed to an adverse childhood environment.
So what kinds of environmental exposures would we really say should be guided by genetic background? This makes sense when the environment is really a pharmaceutical treatment, ie drug A versus drug B, but when the environment is a larger social context - when does it make sense? I'm not quite sure where the boundaries are here, and I think it's an issue that social inequalities researchers need to struggle with.
One reason I find GxE stories interesting is that they challenge a blame the victim story, the the notion that, because some people have good health despite adverse social environments, everyone could have good health if they were just more determined or did whatever those resilient people do. But I have definitely had social epi people firmly reject my perspective on this and argue GxE research basically takes the emphasis off of the modifiable environmental or social determinants of health.