The Chrome Web Store already blocks any extension with the ability to download videos from Youtube with the excuse of it "enabling piracy." Ironic considering that they allow downloaders for any other site. Only Youtube.com is banned. It smells like anti-competitive behavior to me.
Honestly though, it will come and it will be in a form of copyright infringement, or something vague like that.
Good luck. Don't build your castle on top of another castle.