Obviously this is a sore topic to some people. I have always believed that if you are a PPL holder and trying to get hours for a CPL you will at some stage do some flying for free. I obviously don't support the CPL pilots working for free as there is no benefit in it (except the operator gaining a bigger profit margin).
If you were a young pilot trying to gain the hours for a CPL you have 2 choices; pay for that flying or take up someones offer for free flying. If you way it up logically the cheapest a/c hire at the moment (and I'm just guessing here because I haven't done it in many years lol) would be a couple hundred an hour. So lets say as an argument that you were going to pay $200 for an hour in an aircraft and someone offered you an hour for free, then you are getting the hour and keeping that $200 in the bank. I think this is a fair deal.
That being said I think it is up to the individual to weigh up the options here as there are some undesirable operators out there that abuse this system.