The dream's now real - you can upload images from your DSi to Facebook.
Provided, according to this Kotaku story, that you live in the US and aren't aged under 13. The feature's already gone live in Japan.
If you live outside the US or Japan, or are aged under 13, you can still use a computer to update Facebook images. Just in case you were worried about that.
See a video of it working after the break.