They can't!

And then even if the project is legit, it could still fail. The project could have been started by people that intend to pay the bounty in full but if the token doesn't take off everyone will be sunk.

All you can do is evaluate all known information about the project and take a leap of faith if you think the risk is worthy for the potential reward.

A few tips to help you:

• Is the utility purpose of the token one that will benefit people that aren't already involved the crypto community as a speculator?
• Does the developer website provide sufficient detail on the business case, the mining approach, the IPO for the token?
• Does the bounty pay in Bitcoin AND not ask you for an up front investment?

If you answered "Yes!" to all of these questions, honestly, then the campaign is a candidate for consideration - NOT necessarily a good option, but worthy of consideration. Good luck to you.