We're building a platform called 'Sunfish' which will make sharing and tagging files a lot easier. The early version of that will be ready in July.
Sunfish is going to be an open source file tracker, anybody is going to be able to run their own sunfish server, and the GUI will have support for pointing at custom sunfish instances.
Would it be possible to put sunfish into the wallet and build it using sia so it too is decentralized? Otherwise centralized file trackers could lead to possible censorship.
It's not hard to envision a DHT where you ask your peers for the file with a given hash, etc. But as of now there are no plans to add such functionality. Separate servers are nice because they can be completely separate from Sia, whereas a DHT would essentially require that we force peers to "opt-in" by default, or else risk low participation.