This is the beginning of the Big Churn. Less top talent will want to be associated with facebook. Already even a few more privacy clueless friends family members are deleting their accounts. Adverts were always so low yeild, and fb pages 'because we need one'. Now that is all changing due to perception. The FTC, stocks falling, are further indicatuons of falling trust. And all business is built on trust.
Oh please - the overreaction from this is ridiculous. I'm buying FB call options. Facebook's network effect is extremely strong - this is also not even including their other assets (Instagram, Whatsapp, Oculus). The API access was in violation of terms of service and the ability to access data through friends via the FB graph has already been closed.
Network effects are not as strong as you might think. Multiple lines of evidence point to it being O(n log(n)) in general. See https://spectrum.ieee.org/computing/networks/metcalfes-law-i... for details.
The log(n) factor does work in Facebook's favor against newcomers. It is a barrier to entry. However it is a barrier to entry that can be overcome with a better user experience.
My desired experience is that I want to see what my friends have to say, and don't want to see random commercial spam. My Facebook feed includes crap from any time I liked a viral link, and DOES NOT include a significant fraction of what my friends had to say. It is very far from my desired experience.
I already see people trying out alternatives like Mastadon. Existing chat applications like Slack and Discord could be turned into social networks. And properties like Instagram and Whatsapp stand as demonstrations that social networks are more easily started than you might think. Facebook can only keep buying up its potential competitors for so long until it runs across one that dreams of something bigger than Facebook can offer.
Short term I believe that there is an overreaction to news. But long-term, I would not want to bet on Facebook. Not over the next 20 years.