Hadn't seen Vidyard before. That's a brilliant business model. Lots of people don't want all sorts of stuff crapping up their content. Plus, it's a perfect example of flying underneath Google. Google is not going to give up advertising any time soon. If Vidyard get big enough, Google can always buy them out and re-brand them as YouTube "premium" or slide them into their google apps for enterprise.
Three of the five, by my debatable assessment, use technology to have a direct impact on human lives. Really impressed to see YC going after "stuff that matters".