It's the potential. You have literally millions of computers on the internet right now, capable of running this code.
Also, raytracing is only an example. But what large data set do you need for raytracing? I guess if you had a massive mesh then that might add up/
4chan is basically a "paging channel" or "advertisement channel": anybody can post, which means it can't provide reliable delivery (any message can be swamped by spam) or archival, but that's the only way to establish communication between people who don't have a pre-existing relationship (either directly or through their social network).
Poisoning/controversy is inherent in human-readable, non-centrally allocated, shared namespaces. (See Zooko's triangle.) It's not always a problem — Google shows that your suggested approach of using a trust network to choose among the candidate versions can work pretty well — but in the cases where it is a problem, you can reduce the magnitude of the problem by using self-certifying names (like SHA1 sums), unshared namespaces (like petnames), or centrally-allocated names (like DNS). Nick Szabo's "Secure Property Titles" proposal is the only plausible alternative I've seen. (I don't know enough about social dynamics to predict whether it would work as he predicts.)
One of the advantages of hash-addressed data (data named with a self-certifying name that consists of a secure hash of its contents) is that it can be replicated to many peers without any particular concern for integrity or timeliness. (And in Freenet and BitTorrent, it is.) So it might be good to use hash-addressed data for as much of the system as possible. Localhost only stores filenames in directory nodes, then uses Kademlia to look up the .torrent infohashes associated with various versions of the filename; it would be good to often provide durable links consisting of the infohash itself.
The other thing I think is needed is a way to publish a mutable resource that only you can update. Such a resource can have a self-certifying (but non-human-readable) name consisting of the hash of your public key, possibly an ID number, and a timestamp.
Localhost, for those who are wondering what we're talking about: http://p2p.cs.mu.oz.au/software/Localhost/thesis.pdf
Try ctrl-h on your keyboard.
Pressing the backspace key on a computer terminal would generate the ASCII code 08, BS or Backspace, which would delete the preceding character. That control code could also be accessed by pressing Control-H, as H is the eighth letter of the Latin alphabet. Terminals which did not have the backspace code mapped to the function of moving the cursor backwards and deleting the preceding character would display the symbols ^H (caret, H — see Caret notation) when the backspace key was pressed. This sequence is still used humorously for epanorthosis by computer literates, denoting the deletion of a pretended blunder, much like overstriking.
Example: My slave-dri^H^H^H^H^H^H^H^H^Hboss decided to stall the project.