Not hugely different from record companies, and many other agency style markets.
Exactly. The fault here is that people turned over their videos, etc to these marketing companies without doing their due diligence and checking to see if these were legitimate and viable companies and with nothing more than a promise of
future profits. ANYONE can call themselves a marketing company and if you're foolish enough to sign over your property, including your intellectual property, to them without verifying their standing then you're most likely going to be disappointed with the outcome.