“There is really no risk to to sharing it,” Rey Junco, a fellow at Harvard’s Berkman Center for Internet & Society, told NBC News.It doesn’t take that much effort to copy, paste and share something. If it turns out to be false, there are no negative consequences (aside from annoying your friends). If it’s true, you get money from Zuckerberg.

Source: Why Do People Believe the Mark Zuckerberg Money Giveaway Hoax? – NBC News