However, I found the most interesting link the one about open salaries [1] - are there any other businesses doing similar things? I'd be inclined to consider it a very strong mark in their favour as a workplace.
[1] https://open.bufferapp.com/introducing-open-salaries-at-buff...
So this trend would shift the cards to the employer unreasonably AFAICT, working to keep salaries suppressed.
Remember that when posting for a new position, salaries are pegged to prevalent market rates. Even bad negotiators as a result benefit from the upward pressure on salaries introduced by good negotiators. If all companies started fixing salaries (which is so far the only way I've seen open salaries implemented), a lot of upward pressure on salaries would be removed, harming all employees, not just the good negotiators.
I am only aware of Balanced Payments that used to have it, but unfortunately they've recently shut down.
Chad Whitacre of Gratipay may know if any other companies do this by now.