Ashley, I'd say you haven't spotted what could be determined, by some at least, to be abuse, because you haven't been in the "system" long enough. Usually by the time it becomes more apparent, people are nearing or at the shodan level, and certainly around the sandan level. By that point you have people who've invested so much of their time and effort learning an "art" that the idea of freely leaving often implies - at least initially - that their practice and progress would grind to a halt.
Dan, while you are correct in that I only have 2 years of experience in Aikido, encompassing 3 dojos and 2 different organizations, I do have extensive experience in Karate. I have also done a fair bit of dojo shopping since I move around quite a bit, and I have seen many dojos that I would classify as abusive in one way or another. What I have is a firm grounding in what is acceptable and what is not acceptable in terms of my needs for study. I also have no problems with taking a few years off of martial arts because I am not willing to study at a dojo that is full of ego, or otherwise an environment I don't find acceptable. While I realize that some students may be willing to put up with abuse just so they are able to study, I am not that kind of student. And even those students are not in the same position at students in college sports. The student at an abusive dojo, no matter what their personal investment in that particular organization, is still free to leave with no consequences beyond their own desires. A student in college sports does not have the same ability to quit, because the fact that the majority of them are on scholarships and would otherwise be unable to continue their college education if they quit dealing with an abusive coach.
I will agree that both dojo environments and college sports can be fertile grounds for abuse, I think it is due to different reasons.