So, I recently talked to Shawn (the Storj founder) and from what I understand, we are a lot farther along in the development process than they are. We use a proof-of-work blockchain to enforce all of our contracts, they don't - they only use the blockchain when it is necessary. We have our completely separate blockchain, where they are using counterparty on Bitcoin. One of the biggest elements is scaling. The amount that we can scale is limited by the amount of data we can put on the blockchain. Using a lot of payment-channel style optimizations, we can get somewhere between 20k and 1 million users to fit on Sia given the current technology stack. Once we're over 1 million users, we'll have to find something else.

I'm not sure how well Storj will scale, but their test group A showed that they needed to improve a lot of things. They believe that test group B is still a few months away. We are launching on June 7th.

One of the biggest differences between Sia and Storj is that Sia intentionally stayed off the radar (we've actually been around longer than Storj - Sia was originally invented at Hack MIT in 2013) until we had something to show everybody. We surfaced briefly to do a crowd fund because we were broke. We're now ready to rock and roll, and we have a client that is functional. We also have a very clear roadmap for the next 3 months, and I believe we'll be a satisfactory replacement for Bittorrent by the end of the year. The current 500mb filesize limit should be raised to well over 1TB by August.

If you are curious, you should try out the beta and tell us what you think.

I'm not sure if Storj plans on having an API, but Sia has an API that other apps and decentralized apps can hook into for decentralized storage. Imagine if XBMC started streaming movies and music off of Sia. And imagine if Streamium used Sia to put streams in an archive. These are both things that are already possible using our API, so long as you keep files below 500mb. (and again, this limit is going to be lifted in the next few months).

I hope this helps. We think that there's a lot to love about Sia.