Will using 301 redirects to reduce duplicate content on a massive scale within a domain hurt the site?

[Silkstream]

We have a site that is suffering a duplicate content problem. To help resolve this we intend to reduce the amount of landing pages within the site. There are a HUGE amount of pages.

We have identified the potential to reduce the pages by half at first by combing the top level directories, as we believe they are semantically similar enough that they no longer warrant being seperated.
For instance: Mobile Phones & Mobile Tablets (Its not mobile devices).

We want to remove this directory path and 301 these pages to the others, then rewrite the content to include both phones and tablets on the same landing page.

Question: Would a massive amount of 301's (over 100,000) cause any harm to the general health of the website? Would it affect the authority? We are also considering just severing them from the site, leaving them indexed but not crawlable from the site, to try and maintain a smooth transition. We dont want traffic to tank.

Has anyone performed anything similar? Id be interested to hear all opinions. Thanks!

[AlanMosley]

I would look at your links coming into those pages, and 301 the links only, I doubt all 100,000 pages have links.

A 301 only redirects link juice, so if no external links no problem, of cause you need to change your internal links. You should never 301 internal  as 301's leak link juice, you should fix your internal links.

[Silkstream]

Thanks Alan.I Take it by this you mean we should only 301 redirect pages with valuable links and forget the rest?

The pages dont have any links worth worrying about as its the "weaker" half of the site. We're more concerned over the site restructure and the affecting the general health of the site by losing so many pages at once.

[AlanMosley]

Yes that's correct

The pages will be found just as quick thought there new links as they would have been though their old links with 301's