HR at my last place was very aggressive in reminding us to leave 5-star reviews at Glassdoor. They once even offered Starbucks gift cards to the first 5 of the month. I was very sure to leave an honest, dirty laundry review after I left including a mention of this practice

Wouldn't what they were doing be against the ToS of places like Glassdoor?

Probably, but does anyone think Glassdoor is going to chase after potential revenue streams for violating their ToS?