I don't know. I'd only be okay with it if it didn't post things to my wall automatically like some sites do. I'm not sure how much traffic it would actually bring in. Most people I know get annoyed by people who keep posting game things to their walls, and they tend to not pay much attention to them if they don't just hide their posts entirely. I hide people who constantly post game updates, and a number of others likely do as well.
Also, the fact that Youtube makes you sign in with your google account brings me much rage since my main youtube account is linked to different account than my main google docs so I have constantly be switching between accounts to use either google docs or youtube. If Newgrounds were to get Facebook linked, you would need to be able to link your account to your Facebook or else it would annoying.
But really, if it actually happened, I would care very little.