Robert_Charlton - 1:01 am on Jul 22, 2010 (gmt 0)
But if we keep those listings in noindex, how can it harm the site?
I do not expect any help by getting these pages indexed. I am more concerned about any negative effect of these pages being in noindex and links to these pages in nofollow.
curioustoddler - For purposes of discussion, I've put your last two comments above together.
I've got to confess that I'm not quite following the syntax of your last comment... but my thoughts, which I hope address your concerns, are that putting the listings in "noindex" will not help your site... and I'm not sure why you'd want to them out of the index, even if they were duplicates of other agents' listings.
At worst, these listings simply would not rank for your domain... but the noindex robots tag would assure that. It's remotely possible that one of these listings might rank on your domain for a relevant search and might attract a click in the serps. This isn't what you're pushing, but I don't see how the traffic could hurt you. It might get someone browsing in your site. Why go to any trouble to prevent that unlikely but nevertheless desirable behavior?
I don't think the pages dilute "theme", eg, nor do I think they'll cause Google to somehow lower the quality profile of your site or whatever it is that concerns you.
As long as they're on your site, the pages are going to divert some PageRank. Making them a robots meta "noindex" will not improve that situation.
Re what I think is the crux of your concerns... I don't believe the meta robots "noindex" tag on the page will help more pages to be crawled, but at least it won't prevent PR to the pages from being recirculated in your site, so it's the least intrusive of approaches available. You also should not "nofollow" links from these pages.
My view is that if you want to regain the PR and crawl budget that these pages divert, then the only way you can completely do that is to delete the pages from your site and delete the links to the pages from your navigation.
If you keep the pages on your site, though, you can and should make them "less important"... ie, minimize the PageRank diversion to them by shunting them off to a side subcategory from a location page that's low in your top-down hierarchy.