The best way to curb this scams is people becoming more alert when on the internet, take everything as a scam until proven otherwise, this way you approach any offer with a certain level of skepticism and are less likely to fall blindly for cheap scam attempts.
Or just used your common sense, as no one will really give us free money here, not even the rich and the famous. We really don't know the numbers, but many are still falling for this trick and scammers are very satisfied with the results because they know that a person greed is really hard to resists until it's too late.
Here's another one: