What a pessimist. You're assuming or at least making it sound like madysmom doesn't do any maintenance. If this is the case then evaporation will cause the salinity to rise and overcome any loss due to salt creep.
As far as having a negative effect on corals and fish, a few bubbles won't hurt anything. Lots of corals and fish live in the surf zone and are naturally exposed to a lot more are than what a diffuser can produce.
Don't get stuck on one philosophy of fish keeping, there have been many successful styles and combinations throughout the years. One of the first successful reef aquariums belonged to Dr. Eng back in the 60's. We didn't have the understanding of reef aquariums back then as we do now. Most of us who attempted SWF used crush coral or oyster with a undergravel filter and maybe a 15 watt light. His aquarium was filled with sand, rock, plants, and various animals, it was lit by natural lighting and used a air diffuser for surface movement. He was able to keep animals that were considered impossible at that time. We have come a long way since then and I'm sure we will go a lot further as we learn even more about the animals that we keep.