Surprised no one has mention it yet, but Recruit Holdings is the parent company of Indeed.
So the combination of Indeed's set of basically every job listing and Glassdoor's set of reviews seems like a strong synergy to fight against Google and Facebook's move into the space.
Indeed/Recruit has made several big acquisitions in the past year including SimplyHired and Workopolis.
Note: I founded/work at a startup in the same space.