Homemade 3D porn, obviously.

I think that this could be a big deal. Nintendo could offer a YouTube style channel for users to upload their 3D videos. If they worked this correctly it could be a huge selling feature. Of course 3D chat will be impossible since you couldn't see the screen while chatting, also I see Vita has announced that you can record game sessions with your face and game play footage. Nintendo could easily offer a similar feature and this could increase the ability of Nintendo to compete.

3D video is definitely going to be a selling feature. Also with the next 3DS model they could improve the quality of the camera which would drive many people to buy one. Lets face it their aren't that many affordable 3D camera's out there and 3DS will give consumers that ability for cheap.

I think this feature will most definitely be used. If Nintendo markets it right it could become one of the 3DS's biggest selling features!

"3D video is definitely going to be a selling feature."

It hasn't been selling that well for movies, and 3D box office is falling. So there is little reason to think people will leap on it for the 3DS.

2D is just as easy to do, and has greater compatibility for recording, editing, and playback.

It's a nice selling point if Nintendo manage to get it right. As a standalone feature, it probably won't do much good, but if Nintendo manage to create the right ecosystem integration, it could be a big plus for a part of their audience I think. Here's what I think it needs to be succesful:

1) YouTube 3D compatibility (easy upload of 3D videos and seamless viewing of other 3D videos on youtube)
2) Augmented reality compatibility (allow people to record 3D videos with their Miis and what not)
3) Basic video editing (minimum)

The YouTube 3D integration is by far the most important part. It's already being integrated into several 3DTVs (via SmartTV apps), so YouTube could be an easy way of making the 3D video recording more than just a simple gimmick.

a longer spec sheet obviously