There are plenty of content sharing apps around. Most of them take the form of a shared bookmark list or something similar.
Spraed is also a content sharing app but primarily for people you interact with in person. Jakob Hoydis, Spraed's CTO, spoke recently at the Couchbase London meet-up about how they'd built Spraed on top of Couchbase Mobile.
In particular, Jakob highlighted that Couchbase Mobile's syncing enabled them to build Spraed much more quickly and with a smaller team than if they'd had to build syncing themselves. He also spoke about how much help they continue to get from the Couchbase Mobile mailing list and what the future holds for Spraed.
Here's the interview that I recorded with Jakob right after the meet-up. I'll be posting the video of Jakob's talk soon.