Withpassion is right! Face pic should be a huge red flag. The only way they can prove is by taking a picture of them holding a paper with thier number. Otherwise they are very likely to be fake.
In rare cases they turn out to be legit. For example Alyssa on BP who is real according to many terb users. She posts face pics on her BP ads.
That's not always true, there are plenty of legit providers who post face pics. I find what's in the background to be helpful in establishing if it's real or not. If it's some well decorated room with expensive looking furnishings, chances are it's someones Instagram. If it's a hotel room, it's more likely to be real. Not always but more likely. You always need to do image and number searches as well as check the forums(due diligence).That being said, it's always nice when they make the effort to prove their identify with a piece of paper. But then again sometimes you just say the hell with it and go check it out, you can always walk away