The key word being "unpaid work". Interviewers should be required to pay at least minimum wage for any time taken up by an interview. Better companies will pay

The key word being "unpaid work". Interviewers should be required to pay at least minimum wage for any time taken up by an interview. Better companies will pay better rates. Problem with "work assignments" like this is that there is completely assymetric skin in the game on this. I don't know if you have sent this same task to 1000 other people or just 3. If everyone who did the interview was being paid, you can at least assume that they are moderately serious about your chance of joining the company.