It's not even a background, really. It's pretty explicitly the absence of a background. Even lighting, no shadows, almost adrift. Not in a bad way. Stephen Smith did a great job of covering this in the May-June issue of Creative COW Magazine, including why it's best to use chroma keys to acheive the look.
The most frequent place you're seeing it these days is the "I'm a Mac" ads. (Check the end of this entry for a great variation.) If you cast your mind back a little further, you might recall the same look in the Apple "switch" campaign. As an Oscar-maniac, I hope you saw the short film with this look in the 2006 Academy Awards show, one of the highlights of what I thought was the best Oscarcast in years.
All from the same guy. The guy who invented the look: Errol Morris.
Almost. While it was common in still photography, it hadn't been used in any meaningful way before he used it for the first time in a short film for the 2002 Oscars.
You may have heard his name before, by the way. He won an Academy Award for the documentary The Fog of War, and has been nominated for others of his films, which include The Thin Blue Line, Mr. Death, Gates of Heaven, and Fast Cheap & Out of Control
Roger Ebert has said, "After twenty years of reviewing films, I haven't found another filmmaker who intrigues me more...Errol Morris is like a magician, and as great a filmmaker as Hitchcock or Fellini."
Mr. Morris is not shy. This quote is on the front page of his website.
I've always been struck that he's also unapologetic for enjoying making commercials, including the Mac Switch and "I'm a Mac" campaigns. You can find dozens and dozens of his commercials at his website. Be sure to check the links in the right margin -- yet dozens more.
These full-frame commercials are what got him the gig making the short film for the 2002 Oscar Award, where he used the white background style for the first time. The short film that opened the show that year instead of the traditional musical number is a whole bunch of folks, famous and not, talking about movies they love.
First, watch it here. I watch it pretty regularly, and it still delights me every time.
Then read the whole tale of how it happened in this AMAAAAAZING New Yorker story.
Just in case you're thinking that reading this might be a waste of your time, here's an excerpt from the article.
The interviews were stacked up, one per half hour, and by mid-morning the schedule was a shambles. Walter Cronkite was [on camera.] Donald Trump was waiting, with mounting impatience, in the wings. Mikhail Gorbachev and entourage were trudging up the stairs. And Iggy Pop was in the greenroom.
You read correctly. Iggy Pop was scheduled to go on after Mikhail Gorbachev, who it turns out is a big Russell Crowe fan. "And anything with Julia Roberts." You think I'm kidding?
BTW, I also put the "schedule was a shambles" quote in there because every one of us in production can relate to that nightmare.
So here's where he talks about that "white background" style for the Oscar film.
I interviewed over a hundred people on a white background....Of course, I'm not the first person to film someone on a white background. It's been done by a whole number of photographers, August Sander, Avedon, etc. I have no patent, no trademark, on shooting someone on a white background. Of course, when you try to do something that's free of artifice, somehow that becomes artificial as well.
(Although I can't find it online, here's an article in the Hollywood reporter talking about it, again, very much worth your time to read.)
The white background isn't the reason that that Oscar short, as well as the Switch and I'm a Mac ads, among others that he's done, so compelling. It's the way that people look so directly and comfortably into the camera. To acheive that, he's created a device he affectionately calls The Interrortron. It's like a teleprompter, but instead of text, it superimposes his face in front of the lens.
Soon after the Mac Switch campaign, he applied the same white background style to a series of political ads for MoveOn.org that also played on his own site. They were a variation on the switch campaign if you will: dozens of people who voted for Bush in 2000, but were voting for Kerry in 2004. Darn near none of them was happy about it either, but they felt compelled by their consciences to switch anyway.
When we first discussed shooting [them], my producers and I would have endless discussions about the way to shoot these political ads, what the appropriate way of doing it might be. Should the lighting be absolutely flat? Should the background be white?...But I like the idea that there's something very straightforward about the ads....
So no matter how you feel about either of those candidates, take a look at political advertising at its best. (Sez me.) And again, lots of related links in the right margin.
After watching the spots, you might think you've got his politics pegged, and maybe you do, but it's more complicated than that. He bumped into Karl Rove in a Hilton breakfast room in Waco. I introduced myself. I said, "I'm Errol Morris. I made this film The Fog of War." Karl Rove said, "That's one of my favorite films. I give that as a present to my friends." So it's certainly not that he's incapable of accurately representing what people say across the range of political experience.
That's really the power of The Fog of War, and an example of how startling it is to look someone in the eye, really look. McNamara's clarity is startling, an experience you won't forget.
I could keep yammering about it, but I'll spare you that to show you this, six of Fog of War's strongest minutes.
As deeply visceral a reaction it provokes while watching it, Morris has little confidence that much will happen as a result of his work.
I think we're rudderless bumblers, regardless of what we might imagine. You can think of my films as cautionary tales, but you might even think of them as despairing tales, because at least in a cautionary tale, you have this idea that by listening to the story you can assure a better outcome. Whereas I'm not at all convinced that's the case. In fact, if anything, I'm convinced that it's the opposite.
That's from an interview in a magazine called, appropriately enough, Stop Smiling. Still, there's a reason he keeps going.
My interest is primarily in what people are saying, and in not detracting or distracting from what they're saying, because that's at the center of what I'm doing.
That perspective, applied across all the work he does, and his strong visual style, are a few reasons among many why I agree with our man Roger that Morris is among the most important filmmakers -- and commercial-makers -- of our time.
And you thought this was going to be an article about keying. 
PS. Xavier Reivax made a short film called "Same" that matches Nine Inch Nails' "Every Day is Exactly the Same" with film footage, the largest source of which is The Fog of War. A very nice combination for both of them.
PPS. On the I'm a Mac ads, your pal and mine Eric Bliss sent me this GREAT picture:

Errol is huge. For me in the
Errol is huge. For me in the battle for best documentary "Fast cheap..." and "Fog of war" tie with Geoffery Reggio's "Anima Mundi" - which also has a soundtrack by Phillip Glass.
But first place goes to "Animals are beautiful people" by Jamie Uys