Think of the list of things you wouldn't want your competitors to know about you - your upcoming deals, your plans for growth - these are things that I've seen founders reveal on stage during a video-recorded pitch competition.
To preemptively answer your question, yes, I am a founder. Yes, I have pitched at video-recorded pitch sessions (though admittedly not ones as high profile as Distrupt). I have even told a judge "we are not ready to share that detail publicly, but I would be happy to share at least some of that information with you after the event".
If you can't share at least some of the basics, then don't pitch at such an event. They are not a fit for everyone, and if you are a speed play -- relying only on first mover advantage-- then they are probably not for you. I personally feel strongly that most founders are too stealthy and too cagey. We should be able to share at least the core of what we are doing because it is a good way to get feedback. The risk is that someone will come in and out-execute you. If that happens, then it was probably going to happen anyway.
Again, I didn't defend the right of the event/moderator/crowd to get a startup's data. But they have the right to ask for it, just like a founder has the right to refuse to give it up.
Startup events operate under an implicit or explicit give-and-take model. You get exposure in return for giving up insightful data about your startup. If you're not comfortable giving away data, by all means don't. But don't expect all other startups at such events to do the same. Let each one decide for themselves?