It seems to me that there is a dwindling supply of common knowledge. I could be wrong, but the more I talk to those only a bit younger than me, the less commonly known are the facts I had assumed everyone knew.
I can't make reference to Rorschach tests, Schrodinger's Cat, Atlas Shrugged, any Constitutional amendment after the first, or various other things without several quizzical looks and the need for long explanations. Spelling and grammar are lost arts, it seems. The apostrophe has invaded plurals and the semicolon has virtually disappeared.
If I start to talk about my favorite authors, some may have read the notes on a work or two; they are more interested, though, in whether I caught the latest episode of whatever's on TV. I'm far more likely to run across someone whose parents read Grisham than I am to run across someone who has ever read a book by choice.
It wasn't that long ago that I thought most people had been exposed to physics, math, literature, biology, history, and politics. Turns out they know a little about gravity, some addition and subtraction, how to read the TV Guide, enough about anatomy to reproduce, what happened in reruns of their favorite shows, and that Bush is President. Beyond that, I can't really assume much.
I may just be far more cynical than is necessary, but it's getting ridiculously frustrating to have to explain references I had once thought everyone knew. Newspeak, Alexander Hamilton's famous duel with Aaron Burr, and special relativity should all be at least familiar to college students these days, right?
I sure hope that working away from a university environment won't exacerbate this problem...