Why are there so many scam bounties out there and how are we to know which is scam or not
Choosing a bounty is depend on your research for picking them because they won't tell you to join on their bounty its up to you to decide and taking the risk of it.
It is very difficult to determine a quality bounty at this time, even when ico successfully reaches the hardcap team forgets the bounty hunter and does not pay bounty or delay the exchange.
CTA, Kepler is an example of a successful project but the bounty hunter gets nothing.
Yes, till now we didn't get the payments from those companies. Really before they seem to be very impressive in all the channels but after the conclusion of the ICO, they have disabled to telegram group which bounty hunters cannot able to ask questions. That's why many people have lost their faith towards the bounty campaign.