no index for archives and tags????? Yes or no?

Using the all in one SEO Plug in. I have the option of setting it to 'no index' for archives and tags. Some have said that this will reduce the amount of duplicate content on the blog - which may or may not be a good thing (I don't want to revisit that debate, thanks).

so do you guys suggest no index for archives and tags, or go ahead and index it???

Actually,now that I'm looking at this closer, the same question applies to categories - should they be indexed too? I'm guessing the answer to this on is YES, especially if you use keywords for category names.