The bad thing is that the 100mW is probably only half as bright as the 1W and unbelievably less likely to injure your eye.
Based on Sony's safety data sheets on laser safety, I am of the opinion that >500mW is where things turn from pretty dangerous to REALLY dangerous.
Yeah, you can get injured from 100mW, but you also stand a good chance of getting a very temporary injury or avoiding injury altogether unless it is a very direct hit.
At 1 Watt, the odds change radically. Now the same accident will almost certainly cause instant, permanent injury to one, or both of your eyes.
>5mW
I let my 3 and 4 year-olds play with a 3mW (metered by me) 635nm supervised by me or my wife.
It is funny, when I show friends my lasers they always ask, "What are these FOR?"
I give them a quick star pointer demonstration (Orion and Sirius are up right now) and then I grin and say, "basically they are toys!"
Definitely a blind spot in his eye anyway!
And i will still buy a 1W laser...