In a good way, obviously. Facebook CEO Mark Zuckerberg highlighted Spotify as one of the companies making best use of the social network’s developer platform, during an on-stage interview at the TechCrunch Disrupt conference in San Francisco tonight.

“Spotify is killing it,” he said, while also citing Airbnb, Nike and RunKeeper as good examples. But music was less of a theme in the 25-minute interview than mobile.

“A lot of the energy of the ecosystem is not going towards building desktop stuff any more, it’s going towards building mobile stuff,” said Zuckerberg. “That’s the future.”

He also pushed back at analyst suggestions that mobile is a big challenge for Facebook, in terms of making money from its rocketing app usage.

“It’s easy for people to underestimate how fundamentally good mobile is for us right now… on a bunch of different levels,” said Zuckerberg. ”Mobile is… there are going to be more users, each user is going to spend more time, and per amount of time that they spend, we’re going to be making more money.”

Zuckerberg also announced during his interview that Instagram, the photo-sharing app that has just been acquired by Facebook, now has 100m registered users.

For a full report of the session, read our sister site The Appside’s liveblog.