Being on the cutoff myself (I'm twenty going on twenty one), I think teens should be allowed on the site as long as they have the appropriate knowledge and appreciation of the 70s, 80s, and 90s and follow the site rules. Besides, what they are living through now pop culturally will one day become retro (shudder....I know). Even though I was born in the later 80s (late 1986), I still got to live for a few years in the 80s and so I appreciate children's cartoons, the music, and the movies from that era.
I also think that the 90s are retro. I remember most of the 90s until about 1998 with great fondness - the cartoons were better, the TV shows were great, and so were the movies. It was a time of peace, and the world was a bit better off than we are now. I spent my elementary and most of my junior high school years in the 90s, so I think it's right that I'm nostalgic about the 90s.
So, yes, I think teens today need a refuge from the ever burdening and terror filled world of today. And this place, which has wonderful people (besides the spammers, of course), is a great place for them to talk about their nostalgic moments from the past.