> 1. ... For distributed systems there are more ways to exploit the APIs and gather data on users.
However there is no global state, users only push-pull feeds of friends and friends of friends. (In part for privacy and in part for performance, you don't need to carry all the data for a social network to be useful)
> 3. GDPR compliance about deleting data is almost impossible in a distributed system.
However that doesn't apply to individuals that aren't providing a public service.
> 4. ... Open source software and distributed software tends to be much harder to use.
Yes, however there has been some exiting discussion around what UX could become possible in a decentralized context. See https://coolguy.website/writing/the-future-will-be-technical...
> 5. Any future concern/issue will be much harder to resolve if there are thousands of different instance running decentralized social networks.
There are no instances, only peers. (Pubs are sort of easy to connect to peers and there is work being done on peer discovery to outdate most pubs; they could still be used to connect communits around topics, hobbies, etc as a way to reduce the distance between peers)
> 6. Using AI to detect abusive content or spot fake news is much harder if you only have a subset of the data.
There is no retweeting/sharing, though there is work being done on Out of Order Messaging to propagate a single message along the follow graph and there is work being done on flagging/tagging feeds/ids and posts. (Along with some semantics around how to interpret the flags/tags to improve UX and user control)