it depends on how you ride it and what your experience level is.
first time you step on a skateboard you've got a near 100% guarantee to bust your ass... the longer you ride the more control you have over yourself and the board.
now, if you ride through city traffic switching lanes, cutting off cars, cutting through pedestrians, riding in the opposite lane, all while lighting a cigarette doing a no handed skid, then yes... you may run a considerably larger risk...not because you dont know what youre doing necessarily, but because you havent only yourself to worry about... youve gotta worry about all the other people on the road as well.
but all of the hazards are not only available to fixed gear riders...these are just hazards of the road regardless of if youre freewheeled or fixed (minus the no handed skid)
ive been riding fixed for a while now and i feel more dangerous on a freewheel than i'll ever feel on a fixed gear. im sure other people will agree upon this... because we've become very well adjusted and familiar with fixed riding...but of course this wasnt the case when we started.
if you dont wanna get hurt, then dont ride like a jackass.
perform proper and thorough maintenance of your bike and be mindful of whats going on around you.