I got rid of the tag's in the sitemap on a handful of my WP tubes last year since the cat's and tags were basically same, didn't seem to help or hurt, other than I have few pages to work on text for SEO. You have to make sure to mark your tag's as noindex so that the google spider doesn't just get them when spidering the site. You'll also want to make sure that you have good content on the pages you do want spidered. If your just pulling data from other sites, and re-posting, getting rid of tags won't help much if google detects that your just an aggregator
