it would be nice if you could turn the functionality on so that you can stop people from spectating the game.

The way I see it, it's in the nature of the site for everything to be out in the open. What I would like, though, is to be able to hide the list of spectators so that you don't get distracted by the knowledge that people are watching.

2 Queens, 1 Pawn
http://lichess.org/@/Just-a-Pawn

I agree mostly as it annoys me like hell when I want to private play against Stockfish or whatever or playing a friendly game I want to be between me and her or him.

Problems is cheaters could potentially use it to their advantage.

Knowing thibault though, it's that open-source, open-site, open-freedom, open-ass, open everything philosophy like tsinnema said that's gonna stop him from wanting to add any of that shit. :D