A lot of Flash dancing silhouettes have started appearing in small Internet ads and they are very arresting (which might explain why they are there).

I suspect the animator who created the figures used stills from a video and did a figure/object from each frame. Slow process but very effective result.

And as this is traditional animation, you don't need to bother about tweening. You just create a bunch of frames.

I believe the term for this in TV commercials is Rotoscope.

Gary