One of the biggest problems is that many teams claim they would have legitimate reasons to stay anonymous. Since that might even be true in some cases, usually it is not but just for the sake of scamming people. It is just hard to differentiate one group from the other.
I have heard the same, but remember that Satoshi remained anon but did not sell a token to someone. Bounties exist for a fun-worthy project and they are selling a product so there lies a difference and the argument to bunk their argument.
Hence it is a gamble, but sticking with reputable bounty managers helps a bit because you know that they do a good bit of due diligence on their own because they don't want to put their reputation on the line for a blatantly obvious scam.
It is worse than a gamble. You are being too generous to these scammers and by doing so you will end up losing money. At least in a fair gambling game you have a chance of winning. Here you are being sold shit tokens of no value in exchange of your valuable bitcoin which is going up everyday.
Managers themselves get scammed by these projects and it is not their fault that the project managed to fool them, embarrassing for them yes, but they are no liable for the losses. Also the same reason why you will rarely see reputed managers take up such projects.