Why is it a big risk? First of all you don’t need to make investments. You just plug a product by doing different tasks like following social media, make up a video about the project or type an article about it, and then you might be paid for it.
Secondly, I strongly believe that if you do a research you will avoid scam projects. You always should go through social media, web-sites and overview the team members.
It's true, the advice you gave is very good and can also be used by those who have social media accounts with a high number of followers, because the pay is definitely high too, be it from websites, youtube accounts, twitter and others.