lorax - 5:09 pm on Jan 30, 2013 (gmt 0)
I wouldn't noindex the product pages unless they're duplicate content.
I think a case could be made both ways (index and noindex) for category level pages (auction listings).
My theory (and it's just my theory of how the SEs might see it) is this. If content (products) are constantly coming onto and leaving the category level then those pages aren't likely to hold much weight for long tail keywords. Instead, they are more likely to have credibility for shorter keyword phrases AND the overall topic the products belong to. This is why categorization is important and why I think it would be better to SEO for the category level.