Someone at work told me how much she was getting paid, it was less than me and I told her, she realised she was being under paid, significantly. She's happier now she's not so stretched financially and the business can easily afford to pay her properly.
I'm not sure people realise that companies will pay you the absolute minimum they can get away with if you let them. If you have no idea what people around you are getting paid then you'll probably end up getting paid less because you won't know where to pitch your value at. If I didn't know what other people were getting, I wouldn't have known what to say my expected salary was and probably would have pitched based on how much I wanted to do the job, rather than what it was worth. I'd have been getting less than I do if I'd had to come up with a number in ignorance.
Knowing what the industry you work in pays someone doing your job has no downside to you.