So where was it announced that Natal would require the 4 meters of space to operate?

Since the Natal camera uses IR sensitive lens coatings, I don't think dark clothes/dark complexion will be an issue.

If anything, dark clothes show up hotter on IR wavelengths as their pigmentation absorbs more light and heat.

Complexion shouldn't matter either as it has minimal bearing on skin temperature as the majority of the heat registering on IR wavelengths if being generated by the body itself rather than what is absorbed by surrounding light.

Anyway, none of this is even finalized and this whole "medium sized room is necessary for Natal" may be an exaggeration.

Of course anyone who thought they'd be playing full body motion games in an 8x10 or smaller room in front of a desk is probably kidding themselves.

The Natal IR sensor is detecting light reflected back from the IR emitter, not small amounts of heat, it isn't that sensitive(although if something is REALLY hot, it will show up).  The little light source from Natal will hopefully not be powerful enought to heat up a black shirt :)   So, the fact that darker pigmentations absorb light, makes it not as good as pigmentation that does not absorb light.  Will it affect it enough that things go awry?  Probably not.

Same concept goes for skin as well.

The IR emitter is a set of LEDs with an IR coating, not much different from the IR emitters used on night optical devices ("night vision goggles") available commercially and even those used by military. They simply provide additional light to enhance non amplified IR sensors. They don't actually have to paint everything with IR light to make objects visible to an IR sensitive lens equipped camera.

What Natal will lack (without actually disassembling one; just able to tell by the cost of the unit) is the amplification tubes used in NODS, making it function more like a consumer video camera with "night mode." Haven't actually played extensively with one of those, but have had quite a bit of experience using NVS 7s and NVS 14s. Warm and dark objects will show up "hotter" even without IR light from the emitter.

Skin emits heat which registers on the IR wavelength and subsequently picked up by cameras with IR sensors, even in the absence of light, regardless of whether IR or visible spectrum. Dark pigments absorb more ambient heat than lighter pigments, making them more visible on the IR spectrum.

But without amplification, Natal probably only registers IR light directly reflected from the emitters, meaning anything that's not properly lit up by the IR LEDs (too far back) might not register at all. So if it only registers reflected IR light, that's an issue that could only be fixed by increasing the gain of the camera sensor that lacks coated amplification tubes.

That's all elementary stuff though. I'm sure the Natal engineers will have worked all those issues out by the time it moves to production.