However, to play devil's advocate I'll ask; what's an appropriate bounty? If one were to offer a bounty of 0.5BTC for testing a service, how unbiased will the reviewer be? At what point does it start to look like something nefarious?
If the bounty is 0.5
BTC it is shady from the start. If you are earning $2000 testing a product you could get inclined focusing on the good stuff and intentionally or not, forget to mention the bad. And that what you forget to mention could end up being a problem for you and any future users of the service.