You're probably referencing this fuck up: https://en.wikipedia.org/wiki/The_DAO_(organization)
The huge advantage of smart contracts is that they are supposed to be trustless - you don't need to necessarily trust your business partners because contract is set in stone ... code and will be executed exactly as agreed beforehand.
In reality, you move your trust in your understanding of the code. But then when 18 000+ (probably highly technical) people investing $50 million don't spot the bug in the code, then it calls the whole "trustless" concept into question.