Forrest the supplemental index originated so that Google could still index pages it considered less important. They claim they’re making it much more like the main index, but if there’s no difference it seems silly to maintain two separate indexes.

My guess is Google wants to keep us from reverse engineering things or maybe people were figuring out how to manipulate ranking based on supplemental results. Since supplemental pages don’t pass link juice maybe Google wants to keep hidden which sites it’s figured out are buying and selling links.

It’s also been suggested that people clicked less on links that were labeled supplemental so perhaps this is simply a way to increase CTR.

In the end we’ll still be able to figure out or guess well which pages of a site are supplemental, but it will be harder and it’s another step in Google holding back useful information. If the do add something to Webmaster Central it might not be so bad.

I have been thinking more and more of moving our blog back to wp at least that way I can have a little more control over this.

Khalid