This is one area where the government needs to step in. Video-hosting websites should be made to flag videos as AI-generated. AI companies should be made to watermark generated content in a hard-to-remove way (i.e. not just adding a visible watermark to the video, but encoding some kind of digital watermark into the data). Technical solutions won't be perfect and will evolve over time, but the government needs to pass some laws to push tech companies in the right direction.
The only companies that'd follow the watermark are the good guys though, yeah?
The people you'd want to be wary of would be the ones that'd look legit.
e.g. "yes i guess i will send my son $400,000 in cash tonight because he's been kidnapped, and i know it's real because there's no AI watermark that all the nice US/EU companies use."