Even everything above is followed correctly, still there's no guarantee that project will be good. However, if someone does enough research it's possible to avoid scam project. I am really bored on bounty and given up participating too.
The most important thing is that we as bounty hunters are constantly trying to find legitimate projects, for me to avoid this kind of thing is to join several campaigns such as blogs or social media in several projects. When I used to have a lot of free time I often did that and there were definitely some projects that would pay.
as a bounty hunter it is really hard for us to this come by some bad projects or trash bounties so for my fellow bounty hunters let's be careful on picking a bounty of things that we are joining or participated because we are already aware that there are some or few scam bounties that are not paying their participants or their bounty hunters and they are just keeping it.
So i suggest to just picky on some bounty campaign so that you will not be able to promote or participate on some bad bounty campaigns.