Joseph Perla explains how Facebook’s business model is built on sand:
Visit this link
Eventually, though, and this might take a long time, but it is finite, everyone will have tried Facebook ads and know that they are useless. Eventually, after 10 million businesses have invested $1000 each, and Facebook has earned $10 billion in revenue in total, then they will have run out of new customers and their revenue will dry up. A useless product is never sustainable.