buckworks - 3:34 pm on Oct 22, 2008 (gmt 0)

duplicate only by virtue that the content management system made the content accessible through a variety of ways of accessing that data

No, it was duplicate because the CMS generated pointlessly redundant pages by presenting large chunks of identical content in multiple locations (different URLs). It would be much better to figure out ways to provide a "variety of ways of accessing" that lead users to the same content on the same URL (or at least fewer URLs than some CMS's generate).

In my experience, there is no problem with duplicate content in the form of single paragraphs or lists of details that end up mixed and matched on different category pages. As long as the resulting pages end up sufficiently different from each other, Google would have no reason to filter any of them. Many businesses might end up listed in more than one category or zip code, for example, but different zips or category pages would end up with a very different mix of listings.

I say the problem is Google's to fix

They do, by filtering out results that they perceive as pointlessly redundant.

fiddlesticks to Google

No comment ...

From the OP:

The plumber links to my IYP once and my IYP links to his website dozens of times.

Then the plumber would see your site as a valuable place to get listed. That is A Good Thing. However, if his link would show up on "dozens" of URLs you should try to tighten up how you're presenting your content so there are fewer URLs involved.