I market for a company with 4 websites that have nearly identical product lines, but are branded differently for different audiences (ie. 1 retail site, 1 discount site, 1 membership site, 1 site for non-profits and their employees). We were told by someone this past week that the search engines might be penalizeing all of our sites in the organic searches due to the similarity of the product listings on the 4 sites. They suggested that we disallow robots on the product pages of the 3 lesser sites in order to increase the organic positions on the main site. Is this good advice, and if so, should I be disallowing all robots to the product pages, or just certain search bots?