Sia has changed substantially since the creation of this thread. Much of the information, especially in the early pages, is incorrect. A new thread has been created here:
https://bitcointalksearch.org/topic/ann-sia-decentralized-storage-1060294Sia is a new cryptocurrency that is being actively developed. We have released a whitepaper, and are in open beta.
About Sia's Technology:Sia is a proof of work blockchain just like Bitcoin. A single feature is added that which enables clients and hosts to make storage contracts that will automatically be enforced by the network. More can be learned by visiting our website and Github page, and by reading our whitepaper (all available from our website).
About Sia's Economic Model:Sia compensates hosts using a cryptocurrency. This cryptocurrency, Siacoin, will be easily exchangeable for bitcoins and subsequently USD. When the currency launches, 10,000 siacoins will be mined per day and distributed to hosts according to the volume of storage they offer to the network. The number of coins mined per day will decrease until the 4 year mark, at which point the network will mine coins such that the annual inflation rate is kept permanently at 5%. No coins will be premined.
Storage can only be rented using siacoins. This presents a major inconvenience for most people, so we will be providing a service that allows users to rent storage with USD, transparently exchanging dollars for siacoins behind the scenes. The siacoins spent on storage go directly to the hosts that hold the file, with the exception of a fee. The fee is distributed among the owners of Sianote. Currently, just under 0.5% of all host income has been distributed/sold/circulated as Sianotes on the Nxt Asset Exchange. The devs are no longer selling sianotes directly, they must be bought on an exchange. More can be found at
www.siacoin.com/sianotes.htmlUse Cases:Since files are spread across hundreds to thousands of machines on Sia, the throughput for downloading a file is expected to be on the order of gigabits per second. Optimized files can enjoy latencies below 100 milliseconds from nearly anywhere in the world (or just on a single continent if the goal is to save money), and low redundancy files can be maintained at slow but highly reliable speeds for much cheaper than existing cloud storage solutions.
Any static data that already gets transferred over the internet would be more efficient through Sia. Every image on the internet could be embedded through Sia. This reduces the workload and bandwidth costs of webservers and makes websites as a whole cheaper to run. The same also applies to videos, which would substantially lower the barrier to entry for video websites. We plan on making Sia javascript and HTML5 friendly, meaning that pretty much any website will be able to integrate with Sia and pull content from Sia.
Sia is also friendly to applications. Imagine a music library that does all streaming directly from Sia. Right now, services such as Spotify and Pandora stream compressed music, because bandwidth costs are high when moving media around. If they streamed the music from Sia however, the costs would be reduced such that streaming FLAC from Sia would be cheaper than streaming mp3 or ogg from their own servers. Imagine video games that manage save files from Sia. Imagine streaming movies from Sia. Imagine downloading applications from Sia instead of sourceforge, a package-manger mirror, or Steam.