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I might be a little different than some of these answers but I would recommend that you exclude them from getting indexed.

The reasons I would do that are that:

You know it is largely duplicate content and goes down to the same pages as your categories.

Google has stated that they would prefer to not have it indexed.

The increasing number of pages indexed will dilute the link juice of the entire site.

There is also the possibility that people using the url bar of their browser will start to increase the number of pages indexed by a large manner.

A competitor could create thousands of links to these pages and create a huge footprint that is search pages.

And finally, I like having product pages ranking highly if at all possible.

I would do this with both the robots.txt file and the GWMT exclusion on /product/search/ directory

Good Luck!

I think it is a little early to do a universal 301 redirect of all of those sites to your main site. Some of my sites affected last month have already started to come back. I would try to continue to get them to come back a bit.

You could get some more topical content on them and maybe clean them up a bit.

Then wait.

If that still does not work and you don't want to maintain or track them you could do 301 redirects. I dont think you will pass any penalties. I have done this myself and did not see any ill effect.

It seems that when penalties happen they tend to be to a directory or a domain. The penalty does not seem to get passed along.

Anyone else seen any bad things happen when a 301 redirect was done?