Let me see if I'm thinking on the right track about potential applications here. First thing I thought of was proactive defense against someone patenting an id

Let me see if I'm thinking on the right track about potential applications here. 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). 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. 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. 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. Disclaimer: not a Bitcoin user, and know practically nothing substantial about it.