if its set up properly and you dont try to spray a huge shot on your stock motor, you'll be fine. i'll be spraying at least 100 on my new PI motor next year. of course, i'll let my tuner do the install and tune it "right" for the juice O0
all the problems i've seen is people using manual switches and shooting at part throttle and not WOT... just get all the safety stuff along with it... and make sure that you use a window switch and set up a little above 3000 so that the velocity won't let fuel puddle in the intake.
the way i look at it it may be a little different but any mod or power adder can and cant be safe. its safe when its setup properly and if its being used properly (note what was said above me) now not safe is when its insall is half ass and used badly sry if im bursting anyones bubble lol but having that feeling where you can jst hit a switch and got crazy power would be a rush ;D