This is common practice. There are many salary surveyors that will collect, anonymize / aggregate and sell back the data to companies. At Levels.fyi we're trying solve issues that typically plague these salary surveys (ex. data staleness, leveling / title normalization, etc). We do this by flipping the model and collecting data directly from employees. We've also mapped levels to a fluid range rather than rigid step-wise increases. Crowdsourcing has it's own challenges (validity, normalization, etc). That said we've had several high-profile employers sign up for our new data subscription: https://www.levels.fyi/offerings/