Sadly it seems you're right about Facebook and being trustable. I see more scammy ads on Facebook than almost anywhere... yes, I do use Facebook quite a bit, mostly because I help manage a business page there. The problem likely is that there's a really long lag time between someone reporting a scam, and the ad actually being taken down. Gives the scammers ample time to "harvest" several thousand dollars before being shut down...

Yeah, the BTC (and other) mining scams also abound.

It's tough times out there, and many people a deperate to get money.