Rather than thinking about it in terms of safety, I always put this one down to awareness - be aware of where you're throwing, being aware of how experienced and breakable uke is etc. Being pedantic (and probably wrong) I know, but safety for me implies a set of imposed restrictions, normally from on high (instructor) while awareness is situational and involves each individual more fully.
On my usual rambling aside, heard a nice version concerning safety from a bjj instructor, they have a policy that if you hurt a uke, you're off the mat for as long as they need to heal and come back - interesting one I felt, wonder how many aikido people would fall afoul of this one.
Bryan, wish him well for me (and tell him off for slacking
)