system
A chat on subreddit /r/wallstreetbets
human
Facebook was revenue negative for a long time, but it always had a clear path to profitability once it hit critical mass. Uber has no such path. The network effect isn't helping Uber as it has helped facebook, because the network does nothing to help you capture a new region. The network in each new city must be rebuilt from scratch every time.

gpt
Risk will always be there, but The network has already established in the majority of US and European cities. Ubers problem isn't a lack of demand or supply. It's revenue, this can be solved by a restructuring of the company or investment in other area. Food delivery, peer to peer car share, bikeshare..