Hiya!
Completely depends on the Player and the Players "mood" that day. For me, as a Player, I like to know stuff about it. Stuff that lets me imagine the scene... colours, smells, and sounds mostly. If the DM can 'paint the picture' by using words that describe aspects to his/her world, I'm in!
Example: "The architecture is very similar to old Baklunish, but many of the onion-dome tops are painted with Keolandish colours and styles". I can imagine that easily. It takes moments for the DM to describe...and the only way I know what it looks like is because I know what the Baklune people of Greyhawk 'are' and what 'Keolandish colours' means. Without that knowledge, the DM would have to take longer to describe, and that description could be used for any D&D world setting.
So yes. I think at least SOME info about the world needs to be presented to...and retained by...the players. If I've been playing with a Player for a few months, and I say "You can barely make out the kilts that the men wear as they sit around the fire, drinking, but the colours indicate a Keolandish clan. One tent, off to the back, displays a single banner, baring the coat of arms from Geoff"...and the player looks at me and says "Huh?"...I die a little inside.

The Players should know that this is...odd. Why? Due to the world history and all that stuff. Players that don't recognize the significance (or potential oddity at any rate) may very well end up in a world of hurt later on. Then I get the "But how were WE to know they were pretending to be soldiers from the Dutchy?"...and I point out the kilts versus banner thing, and they go... "What?! You didn't tell us that was important"...and I point out the handout I gave them three weeks ago that shows the Grand Dutchy of Geoff's banner and the brief, one paragraph, history of why the Dutchy has been so safe...other than that one little 'war' with Keoland. Then they go "Oh...crap...yeah...well...hmmm....".
Bottom line: Some players really get into it. Some don't. Most are somewhere in between. As long as they at least read and keep the notes, hand outs, etc that I give or point them to, I'm happy. The Players who are into the world/history/politics will point stuff out to the "less informed" Players. This plays out nicely in game most of the time, with the supposedly uncultured Barbarian having to explain to the Cleric of Boccob, "How in the Oerth can you be so well-read...yet so obtuse when it comes to the very country you are traveling through?!?".
^_^
Paul L. Ming