its true that doing ico bounty or being a participant in bounty campaign might give you a huge reward. but no all of them are legit, most of them are scam, that's why its better to look for a legit one.
indeed, not all bounty campaigns are legit and guaranteed that will give you an earnings in the end of the campaign, there is a lot of scam campaign and its hard to know if a campaign is legit or scam.