We also stopped describing the video as optional. In practice it wasn't.
Some unsolicited advice for this question:
For startups that rely on 'going viral': The benefit that users get from telling their friends is...
For businesses that need to get 2+ separate-facing user bases: The game theory aligns and makes it rational for both X and Y to participate because...
For startups doing B2B sales: The reason the X will look like a hero to his boss for making this purchase is...
If I were the one reading these I would also add "What's the one thing that needs to happen for this business to become a huge success?" Not only is this (IMHO) necessary to ballpark how likely the business is to succeed, but it's also extremely good at spotlighting both good and sloppy thinking.
i'm assuming "why did you pick this project..." is all about the passion...
Actually the ideal answer would be "We needed this at the last company I worked for."
First of all, many jurisdictions make it hard for employers to try to control things you invent on your own time without using their facilities -- which doesn't keep employers from trying.
Secondly, even if your employer arguably does control the IP you need, that doesn't mean they won't give it up. Woz famously realized that HP had a claim to the Apple I and offered to let them have it; HP thought of it as more of a hobby than a business and the rest is history.
Universities and other research institutes routinely let employees spin off companies, usually in exchange for some share (although, anecdotally, it seems that universities that are new to the game often ask for more than universities that already have strong spin-off cultures).