Yam finance (YAM) is one of them with scam accusations. Early greedy investors can earn profits from scam DeFi but late guys with later scam DeFi projects will suffer loses. They are another way to build up successful scam projects, after privacy coins, ICOs, IEOs. Such scams can not be boomed without endings.

https://cointelegraph.com/news/yam-suffers-technical-outage-following-scam-accusations