Are Blu-ray and HD-DVD Discs Region Coded, Like DVDs?

About.com's Home Theater question of the week is – "Are the next gen formats region coded like the original DVD they are replacing?" The answer is yes for Blu-ray and no region coding for HD DVD.

From the article: 

While the North America, Japan, and Latin America employ an NTSC-based 30 Frames-per-second video system, most of the rest of the world is employs a PAL-based system with 25 frames-per-second. In addition, some of the other technical standards in use for audio processing and video processing could vary.

This means that an HD-DVD disc, even though not region coded, from another part of the World may not necessarily play on a North American HD-DVD player or vice versa.