Let me see if I'm thinking on the right track about potential applications here.<p>First thing I thought of was proactive defense against someone patenting an idea by proving your prior art without necessarily divulging the information (or divulging it, while proving its chronologically prior existence).<p>After that, my mind jumped to media, such as the ability to be provably certain a given piece of media hasn't been altered after the fact (docs, images, contracts, video, audio, etc.), and that it provably existed when a party claims it did.<p>A bit on the nefarious side, I thought of being able to prove the existence of certain media a party wishes to use for blackmail or some other purpose.<p>Maybe applicable to the HN/YC crowd—especially given a certain case that recently made news here about a YC alum—a means of proving the existence of, say, founder agreements when establishing a company, so that protracted legal disputes over ownership could be aided and possibly shortened by irrefutable proof those agreements existed at a particular point in time.<p>Disclaimer: not a Bitcoin user, and know practically nothing substantial about it.