What are some use-cases for this? For example, if I owned a company, I would still want internal data storage within my company, if anything, to save costs on bandwidth. The only applications I can think of (right now) for this kind of distributed storage is similar to what I would upload to dropbox, which is free up to a certain point. And, I suppose, for those concerned about censorship.
We're expecting throughput for a file to be on the order of gigabits per second. Latency on low-redundancy files will be on the order of 100 milliseconds. So, you could theoretically boot your operating system from Sia instead of a local hard drive, given that gigabits per second is close to what SSDs can achieve. The 100 milliseconds isn't typically a problem, but could be for disk-intensive applications.
So the biggest bottleneck is probably the price of bandwidth. If you're a corporation like Google, you probably wouldn't want to use Sia to process search requests, as I'd imagine your bandwidth prices would be too high.
But anything that's already going over a wire would be fair game. Imagine if all images on the web were embedded directly from Sia. This could reduce hosting costs for many companies without degrading the user experience. Especially for video websites, this would be a huge deal. Right now hosting and streaming video is very expensive, and Sia directly addresses these costs without adding any additional expenses with regards to bandwidth. Pretty much any static webpage would also be supported.
Backups like Dropbox are an obvious use case. But applications could also talk directly to Sia. Save-data from video games could use Sia, your music library could stream directly from Sia, and your movie library too if you have a strong enough internet connection.