(n) A well-known person who believes that the world desperately needs to hear their atrociously uninformed opinion on any given subject simply due to the fact they have easy access to the bully pulpit.
This is a word coined by Reverend Marilyn Manson (formerly Brian Warner). As humanitarian describes a devotion to human welfare, "celebritarian" describes a devotion to the needs of a celebrity or idol.
"They orchestrated dramatic new scenes, for celebritarian needs" - "The Fall of Adam" (Track 17), "Holy Wood (In the Shadow of the Valley of Death)", 2000.
A person who is famous for, or despite of, being geeky. Coined by Lev Grossman in a Time Magazine review of author and gameshow megawinner Ken Jennings book "Brainiac".
"Ken Jennings--you know, the Mormon computer-programmer celebrinerd who, beginning in 2004, rattled off a record-breaking 74-game Jeopardy! winning streak."