Most people aren't stupid, just ignorant of the risks. If you are going to mix your own cleaners follow the recipe exactly. Don't subsitute ingredients or try to "improve" a recipe unless you know what you're doing.
If you clean a lot, even using commercial products, you should consider doing it outside, throwing a fan in a window, or investing in a good respirator.
I would avoid ammonia in concentrations greater than 10%. IMO the health risks just aren't worth it. Also be aware that ammonia will attack aluminum.