Can Sia censor files stored in it. If I am a political dissident, and a country orders Sia to remove files I have stored there, what will Sia do?
They can't - the files are encrypted, so even if you wanted to order Sia to remove the files, remove what? And how? If it's public, then they may be able to find what hosts it's on and bully them, but Sia has redundancy - they'd have to bully ALL the hosts, who are probably spread out all over the world, in order to get it to be fully removed.
Unnecessary to assume that anyone would have to bully Sia hosts to remove chunks/block uploaders by IP etc etc. Many hosts, especially those running a business based on Sia would willingly and enthusiastically remove content that has been blacklisted by a "reputable" source (read: copyright protection agency etc). Now, there is a problem and that's that not even hosts know what is stored in the encrypted chunks uploaded to them. Blacklists would have to operate on uploaders, i.e. hosts would have to block certain IPs from uploading to them.
"Sia", by the way, does not refer to an entity of any kind. There is Nebulous Labs, which develops and releases Sia code under an open source license. Thus, the question "what will Sia do?" is non-sensical. If the question was "Does Sia implement blacklisting / retroactive removal of files/peers?" then the answer is "Currently, no". I hope the Sia code-base never gets to this point. I don't see why it has to.
Sia is not under any country's jurisdiction. Still, it is entirely probable that hosts in some jurisdictions will have to comply with local laws that prohibits distribution of some kinds of content, under any circumstance eventually perhaps even when the host cannot reasonably know what they are distributing (i.e. cannot claim innocence for any reason). In those cases, the hosts themselves can readily implement their own peer black/whitelists if they so must. This would result in pseudo-private storage network within the global Sia network, where some hosts trusts only a very few other hosts, some hosts trust most except a few, and most hosts don't give a damn.
Oh, and in Edit this comment to Wolf0's answer:
A censor would not have to force ALL hosts to drop disputed content. If a censor knows about a particular file it doesn't like, then it may be in possession of a .sia file which allows the file to be downloaded from the network. That .sia file contains the IP addresses of all hosts that store chunks of the disputed file. This list is only a *subset* of all Sia hosts globally. It would be enough to target these (~20) hosts to make the file inaccessible. As these hosts may be someone's unhardened personal computer, that may not be such a resource intensive task compared to, say, bringing Amazon S3 to its knees. So, in effect, censorship by denial of service would be quite straight forward. For this reason, it would be nice if in the future an uploader can choose its own redundancy (currently hard coded) to make such an attack more difficult (at the price of also resulting in more expensive uploads).
