Some people are claiming up to 80% click fraud on FB.
I’m not going to do all your research for you but here is a starter:
Should Facebook Advertisers Be Conducting Click Fraud Audits?
Used Google and ST FaceBook Click Fraud got me the above URL and many others too. Forbes is even in there.
In so far as your other PPC campaigns, I’ve always concentrated organic searches because nothing is there to prevent what’s happen here with you, and what’s happened to others in the past. I’d rather spend my cash on high quality copywriters and such and take my chances in the SERPS.
Cheers
Dave