I think this is the inevitable fate of all for-profit review sites which become popular.
The incentives just don't align.
* Ask users to sign up for their job seeker plan to see the complete company interview questions/experiences.
* Create an API and charge websites for giving access to their reviews score, salary data etc.
* Charge money for job postings from companies who have decent reviews and want to post on Glassdoor.
* Provide a paid dasbhoard for companies that will give them insights on how to pay employees.
Again, misaligned incentives between one group of users (people) and the other group of users (businesses), while trying to act as a middle-man. The key is that one group of users has the upper hand in terms of 'investment' into the platform.
... until one group (people) grows increasingly disillusioned and skeptical and the other group (businesses) sense an opportunity to start up another iteration and the balance skews towards the other group (people)... until...
So it goes.