from what I understand of Crossfit, it is common to do olympic lifts for time, either against a clock, against other people or trying to beat your previous record. the olympic lifts are technical and NOT appropriate for conditioning purposes, as crossfit seems to use them. you want to do them when you're fresh and focused. so i would say if your crossfit location does this-- then it is unsafe
You'd be hard-pressed to find a facility that isn't making their clients do olympic lifts. This is where it comes into play that people SHOULD make sure that their Crossfit facility has someone who is USAWA certified in teaching proper form on olympic lifting to clients and that it's not left to someone who may well have no idea what they're doing. It doesn't take more than one light barbell snatch that drifts too far backward without the shoulders fixing the bar in place properly before a rotator cuff can blow out, so obviously, the better the technique, the better off trainees will be.
It isn't that one can't do the o-lifts safely without having proper coaching (I never got hurt doing them with my crappy technique even when going for max lifts), but since Crossfit tends to throw people right into the fire and then put them under pressure by making them race against the clock, it can be a recipe for disaster when a novice lifter is trying to make 20 snatches in 90 seconds because he doesn't want to fail on his WOD.
Ideally, anyone who will do the o-lifts would have at least a few weeks of coaching on building ideal technique, but that's counter-productive to the general mission of Crossfit's intense atmosphere of "train hard, train fast", which is why the injury potential is greatly increased.