If bounty hunters did more research before jumping into any project, they would have been making much more and projects with a shady or half cooked business strategy would have stopped hosting bounty campaigns because there is no self respecting hunter that would participate in their campaign, apart from the stuff you mentioned, bounty hunters should evaluate the projects AS IF THEY ARE INVESTING THEIR LAST FUNDS IN IT. This would enable them be careful when choosing a project to promote.
Earlier replies give links and guides how to spot scammed projects and guide how to choose the right one. Most of my token/coins in my portfolio are coming from bounty projects. But until now didn't have value while others did not list yet in the market. You can dig more and research further about them especially the team they shouldn't anonymous. But I believed they will stop to promote if no one bounty hunters join.