Last week, YouTube announced support for videos shot in 4K, a resolution more than four times that of full high-definition. The ideal screen size for 4K is 25 feet; IMAX movies are projected through two 2K projectors.

YouTube’s blog says, “We always want videos on YouTube to be available in the highest quality possible, as creators intend.”

In addition to its solicitude for video creators’ intentions, YouTube may have other motives. Some commentators have speculated that YouTube is “setting itself up to be a distributor of high-quality original content,” which seems plausible, especially with the imminent arrival of Google TV. But most observers have expressed puzzlement about why YouTube is interested in a high-resolution format that requires camera equipment most professional filmmakers can’t afford. YouTube notes, “Video cameras that shoot in 4K aren’t cheap, and projectors that show videos in 4K are typically the size of a small refrigerator.”

The next sentence of YouTube’s announcement, we think, provides the answer: “Watching these videos on YouTube will require super-fast broadband.”

Such as, perhaps, 1 Gbps to the home?