I don't know if anyone posted this already, but as I saw in some flash games/videos sites, I'd like to see here too the option to "turn off the lights" in the game page. This option would make the page turn black all around the flash player and thus much more clean to play the game, people wouldn't need to use advertise block either. It would be a good addition to the site, in my opinion.
I have mixed feelings about this. Youtube once added the feature (a few years ago maybe), but I believe it has since been removed. I don't feel it helps you focus on the videos or games.
It just seems pointless. I think that's why Youtube removed the feature.
But like GhostOfMatrix said, there are add-ons to incorporate the feature.
Yeah Kongregate has that option. I don't see the need since flash games typically don't get played that long so blocking out the other links would be counterproductive. Plus people that play at work won't want it since it'll make it easier to get caught.
I know there are add-on, but it doesn't work properly in the most websites. It's easier to have a option to use in the website than to dig up the internet for this feature.
I believe a lot of people liked the feature on YouTube, I was one of them and I can tell you that from what I could see on my feedback and search. It's true that most of people didn't even notice when it was available because only a few reads YouTube's blog and it wasn't in a major change to the site.