Marcia - 10:49 am on Nov 13, 2006 (gmt 0)

It isn't only a matter of being "good" enough, which can be a perceptual thing, or relevant enough. It's a matter of also being "important" enough, which is a metric that relies on both PR and number of IBLs, adding up to a given link strength for a site.

Keeping it down to a basic, simple level there just has to be enough link "strength" within a site to trickle down through the pages of the site, and that can be relative to its size - and is somewhat controllable, to a degree, through IA (Information Architecture) - and other internal linking factors.

Personally, I've measured the inbound link strength and progression of some small sites and tracked it over time, and what those sites need is exactly what Adam suggested - more quality inbound links. Meantime, if I know that only a certain number of pages will either be indexed altogether or be indexed in the main and not the Supplemental index based on the current PR and/or number of IBLs, then it's up to me to figure out how to route whatever link strength there is to the more valuable sections and/or pages of the site.

There are ways to selectively influence that to a degree - but as they say, the devil is in the details.