Any time there is a power inequality, there is the potential for "abuses" of many kinds. This is human realm, samsaric truth. Work, business, politics, as well as religion, education, even family, etc., in nearly every realm there is power inequality, and therefore the possibility of abuse.
That's why there is great responsibility, on the part of student and teacher, and why there is samaya. And Samaya isn't just what you read in a book, it's really all about relationship. It is equally the responsibility of the Guru, as well. There are definitely examples of failure--we all know that. But there are many examples of success, as well. In the end it comes down entirely to personal responsibilty. That is the factor that determines whether the institution, the tradition, rises or falls.
"Absolute Truth is not an object of analytical discourse or great discriminating wisdom,
It is realized through the blessing grace of the Guru and fortunate Karmic potential.
Like this, mistaken ideas of discriminating wisdom are clarified."
- (Kyabje Bokar Rinpoche, from his summary of "The Ocean of Definitive Meaning")