My mom told us that microwaves are bad for our health due to radiation. I did not want a microwave in my own apartment until I was 20 and my GF just got one.
They're bad in that they'd cook you with enough intensity, but we don't know of other side-effects. Microwaves are not comparable to ionizing radiation like X-rays, gamma rays or ultraviolet light, which can genuinely damage your DNA.