NEW YORK (AP) — Facebook envisions its new Watch feature as TV designed for social media, a place where users comment, like and interact with show creators, stars and each other — and never leave.

It's a potential threat to Twitter, YouTube, Netflix and other services for watching video, including old-fashioned TV. Yet its success is far from guaranteed.

While people watch a lot of videos on Facebook, these are mostly shared by their friends, seen as users scroll down their main news feed.

Getting people to see Facebook as a video service is like Walmart trying to sell high fashion, or McDonal...