1. Platform power: Apple was a key supplier to Facebook in the sense that they provide platform driving a significant % of their Ads revenue. With Apple tightening privacy they have become an indirect but significant threat to Facebook. Google is relatively safe.
2. Threat of substitutes: as seen in Amazon, Ecom platforms are much closer to the customer. Us timer is about to make a purchase. I think over time Advertisers will eventually shift to platforms like amazon, Etsy etc so that can reach the customer right when they are about to make a purchase. Some what same appeal with snap and TikTok.
Overall online ad industry will continue to flourish but will see big changes in who are the big players.