I definitely think about who would be hurt if I am in a grey area. Most often, if it's just some giant corporation, I will not care if I use the rules to my advantage; however, if it's people I can see, like a small business or individuals, I would take care, to make sure everyone was treated fairly.
I hardly ever lie, not sure why lying to strangers would be okay. Tbh, sometimes my husband makes stuff up in conversation and it drives me nuts. I can't stand having to lie to back up his story and we end up getting in a fight over it sometimes. Once, when we wanted to cancel on his parents to drive to their house for dinner, he told them that our car broke down, and pretended that we were stuck on the road. It was so weird. After a week of pretending, I just felt so bad, I ended up telling them the truth, but at that point, I don't think they believed me.
It does go to show you how different people's moral compasses can be.