I think social bookmarking would work really well with ActivityPub. I recently read a blog post by @daniel@daniel.priv.no about del.icio.us being the web’s discovery-engine of the early 2000s and I think I agree. I also miss discovering interesting posts or obscure websites from people I don't know or "follow". Now that most tech people are starting to appreciate the value of the fediverse, it might be a good time for a community to grow around the idea of social bookmarking again but with ActivityPub and federated servers this time, running a simple del.icio.us-like piece of software (self-hosted or saas).