It's true and many users had scammed, this is one problem in bitcoin trust and security.
We have to do some research before join in such sites, who's the devs team (man behind the project).
Easier if they have good reputation, if they haven't then be cautious to deposit so much, just a little bit that you could afford to lose it is safer.
A trustworthy company is not immune from scam, it is pure market speculation. There should be a system of escrow or breakthrough that oversees it. As long as there is no punishment, these companies will just change the name and office with almost the same system.
For now we can only predict the return on investment, if successful, we were lucky.