Well I can't say that I'm surprised but I don't like the idea of simply dropping the label.
Eary this year (i believe) Matt intimated that he thought the trend for 2007 would be for Google to start looking into the SI when they didn't find enough "good" matches in the RI for a query. Take a 3 word query for example. If Google was not able to find enough pages that contained all 3 words they'd then look into the SI for for pages that did, something that was not being done in the past. This is where the more and more SI pages showing up in regular search results comment is coming from IMO.
Additionally, as I have been watching, pages in the SI appear to be having less and less "value". I've noted that pulling a page out of the SI has had a dramatic effect on the page it is intended to target.
I said I'm not surprised because Google likely sees it at a means for webmasters to try and "manipulate" the pages that they want to have in the RI currently. This is adverse to what's been said about their thinking of what they want their "main index" to be. More comprehensive. More sites represented. Given that I'm of the firm belief that Google has decided to keep their forward index at a finite size, the supplemental label gives webmasters an opportunity to try and force more of "their" pages into the RI at the expense of other pages from other sites.
While I agree with MM that Google should fully parse and index pages in the SI so that they have a "better" chance of ranking, I don't see it as a "fair" chance since they look in the RI first and then the SI if they don't find enough "good" matches. A page in the SI may never even be considered for no other reason than it being in the SI to begin with. If Google were to take the best 20K matches from the RI and then the best 20K matches from the SI for their data set, then the pages in the SI would have a "fair" chance at ranking if they were fully parsed and indexed. To my knowledge, that's not being done.
Personally I see this move as a means for Google to take more control over the pages that are contained in the RI by not allowing webmasters and
SEO's to see and target the ones that are not.
Dave