No. Demo days are where you share semi-publicly your product with investors, other startups, and hopefully media. What is to stop an investor, or other startup, from sharing your demo with anyone? This might even be considered good form, for someone to give the YC alum a heads up, that "Hey, XYZ, is going after your market".
In terms of keyword marketing, I think this is a well known and understood tactic. If your idea/startup is so fragile that someone can market a couple keywords and kill your company -- you have much BIGGER things to worry about!
eh... doubt it had much impact on anything other than just annoying everyone who spotted it. The companies will shake out as they execute.
The bigger question is the DBA (don't be an asshole) philosophy. If you're a fan of mercenary mantra with no rules of engagement, so be it... but you're a jerk. If you win, you get to be a rich jerk. Otherwise, just a jerk.
I recently met the CEO/Founder of Stripe - he was awesome, crushing it, and talked at length about doing the right thing by his people, the world, etc. He's a rich guy that won by kicking ass - not by screwing with other people.
So if you like to be a jerk, create animosity, and contribute to the general consensus that the Valley is about F'ing with each other... then rock on. Otherwise, why not follow the DBA rule and focus on winning investors and customers the old fashion way - being awesome.
No. Demo days are where you share semi-publicly your product with investors, other startups, and hopefully media. What is to stop an investor, or other startup, from sharing your demo with anyone? This might even be considered good form, for someone to give the YC alum a heads up, that "Hey, XYZ, is going after your market".
In terms of keyword marketing, I think this is a well known and understood tactic. If your idea/startup is so fragile that someone can market a couple keywords and kill your company -- you have much BIGGER things to worry about!