Jan Karel Pieterse has recently added an excellent introduction to all this on his site:
Embedding Excel files on your website
Including an example of a user definable animated Lissajous Figure:
Anyone else tried this? How did you find it?
It does seem to be an odd way for MSFT to go about it, but like you said, who am I to question MSFT. I also saw the post on Jan Karel’s site. Both of you have great sites with great quality content.