I have heard about this feature and have also seen on poloniex and rates aren't pretty high and i don't really know how it works and how can it save you from scams. If you want you can instead lend your funds on this forum and you get collateral also. Or instead just trade a few coins on invest in some dice site.
The question is only about lending your bitcoins to make profits and not about investing in other products.
Based on my experience I don't trust any site to manage my funds to give some unknown person because we have heard many scams. So particularly to lend money online I prefer to keep collateral with me in the even if they don't pay back then I can easily liquidate that collateral and get back my money without much hard work. If someone scam on these sites then you need to waste a lot of time to contact their support team to solve the issue.
The fact is that Bitcoin users do not have any legal support. In other words, each user by himself, Although only the administration of those companies or the project where everything is going to solve the problem can. How to protect yourself in case of Bitcoin lending?