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Thank you for your quality comments. I think we are going to go for Evaretts suggestion since I do feel like hundreds of thousands of 301's might be a bad idea. We are also discussing the possibility of keeping the old pages (do index, do follow) up with the old ads, just removing the seller information. We believe that users might well be interested in information about past items sold or expired. This wouldn't require any 301's, just dynamically adding the message suggested by Chris and a search engine/index to help find interesting sold/expired items. This way we could generate hundreds of thousands of content pages which might over time bring plenty of quality traffic to the website. These pages would have dynamically generated fresh content (new suggestions about relevant ads) so I don't feel too worried about old content in Googles index. We could also consider scraping some details of the sold item from the manufacturer website. I've never dealt with this many pages combined with this thin content before so The wrath of the Pand worries me a bit. However the root domain is quite strong and these ads seem to draw quite a few links. The question that requires some further thought is whether or not having this many old, thin pages in Google's index will prove problematic. Thoughts? ps. Since I didn't mention this before, the website is about used cars