I'm a D1 at NYU. We had 238 when our classes started (not including a few that left during Orientation Week), and now we have 223. Of those 15 or so that left, at least 3 I know are coming back to join next year's class - i.e. they are on voluntary leave due to personal reasons. Approximately 10-12 were told to hit the road, if I'm not mistaken.
I personally knew 3 of those 10-12 people that were "kicked out" for academic reasons ("involuntary" departure). All three students had 2+ F's in one given semester.
The few dozen students who had 1 F during the first semester need to remediate those courses over the summer. Only those students who failed 2 or more science courses in one semester are in danger of being asked to leave.
It can be a bit disheartening to see classmates being asked to leave. However, 12 out of ~240 is ~5%, and I would expect attrition to be around 5% for most other schools. Even 2-3 people getting kicked out in a class of 50-60 amounts to 5%, obviously.
I'm probably one of the biggest proponents of NYU you will run into on SDN. Nevertheless, there's no covering up the fact that NYU can be a pretty impersonal and intimidating school unless the student makes a conscious effort to take advantage of opportunities (e.g. in research, assisting in clinic, even simple things like approaching faculty to just sit down and talk, etc). For those that do so, it is a great experience... but for those that do not, it can suck.