But always orders of magnitude slower than what a vanilla CPU can do locally. The value would entail that operations on a remote server are necessary to the function. Maybe a remote database that can be accessed from multiple devices with the same key but still permitting simultaneous read/write operations? The database could be compromised without any data stolen.
Sometimes the benefit from FHE can be larger than the speed gains. Doubt facebook would use this (for scaling and privacy reasons) but if the CIA needed to not have to trust a cloud provider for something of a smaller scale? 100% worth it.
> The value would entail that operations on a remote server are necessary to the function
Yes, not every organization has the compute power necessary, or even prefer to not handle it at all in house. If you only manage keys locally, that's a significantly smaller attack surface.
I'm not sure the value proposition is clear cut. In terms of security, while the server data itself is secure, and the nature of the transactions are inscrutable, there's now reason to share a single key between multiple users, and only one of those users needs to be compromised. The key could be generated and stored in some super secure silicon with a small attack surface, but if the data needs to be available to multiple users, you're back to duplicating and distributing the key, and social engineering remains the best attack vector. A benefit could be gained with multiple users with multiple keys and limited sharing to reduce vulnerability, like sharing sensitive documents between between select individuals. But that's a pretty niche use case.