When two people love each other, but cannot make the relationship work, because their upbringing and backgrounds are too diverse, and they don't have enough experience in common to bond completely.
"Harry and Sheila were perfect for each other except they were Demographically Damned. He could never come up to her level."
From "Zack and Miri"
Brandon: You're not my demographics so I'm notoffended.
Zack: What's your demographics?
Brandon:Do you like pussy?
Zack:I do!
Brandon: Then not you!!
Media slang for daytime television's target audience. Nicknamed for the segment of the population appealed to by commercials running from about 10AM to 5PM. Ads tend to be from industries like for-profit schools (ITT Tech, DeVry), personal injury/tax lawyers (Roni Deutsch, Binder and Binder) and car insurance companies that work with DUIs and tickets (The General, Cost-U-Less). Getting bumped to this timeslot is either the death rattle or a sign of syndication for sitcoms.
"Daytime television, you can tell who’s watching by the three kinds of commercials. Either it’s clinics for drying out drunks. Or it’s law firms who want to settle injury suits. Or it’s schools offering mail-order vocational degrees to make you a bookkeeper. A private detective. Or a locksmith. If you’re watching daytime television, this is your new demographic. You’re a drunk. Or a cripple. Or an idiot. "
Chuck Palahniuk, Haunted
"Jerry Springer just got bumped to the idiot demographic."
Tim: What's the address?
Brian: 4500 North Avenue...
Tim: The North Side?
Brian: Yeah...why?
Tim: Is her name Laqueefa?
Brian: Wow, no it's Carol, Mr. Racist.
Tim: That's not racist, that's demographicalizing
Basically, people (especially teens and adults) who read, watch or play something that's not really intended for their actual age demographic. One example is Harry Potter which was originally intended for children and adolescents but quickly caught on with adults as well.
Hank the Cowdog was originally written for adults, but became incredibly popular with children. That's one example of the periphery demographic stereotype reversed (the stereotype being that most think that adults always read something originally intended for kids, but now it's kids reading something originally intended for adults).