Yeah, it isn't necessarily as easy as it sounds however. On forums you make friends, if you stick around long enough you make a reputation for yourself. People are going to become interested in you, or you will gain interest in others. You'll begin talking more and more, whether it be through PM, or even on the public forum. Some things may just happen where you bring up an inside joke between a 'friend' from the website, or they may spill your full name and what school you go to, without any bad intentions of course.
Those things happen. It isn't easy to stay anonymous on here after so many years, since 2005 I have been posting. I think a point in it comes where you will be known for your real name, etc. It shouldn't happen and doesn't on every forum. There's something different about Newgrounds I guess, any other forum I've been on is totally anonymous for the most part. But you gain relationships through these forums somehow, and one thing leads to another sort of thing.
I regret a lot of my past posts, but I doubt I will lose a job because of it, or get declined a job because of it. If an employer sees my previous posts from years back and sees my posts now. The only notable thing is growing in maturity and seeing things different in a more mature perspective.
Though older posts of mine may seem bad, if you can look past them and see the posts that I make now, the old ones don't matter.
Unfortunately, not many employers or schools will do that though - And it isn't a secret that some schools and employers will end up finding your Newgrounds posts if you have ever had your full name posted on the forums.