Create domains for the user and not the SE. Think about it, as a user, would you like to see 3 unique domains, all showing the same content, filling up the top SERPs? See, duplicate content affects your SERP rankings (this was what the panda was all about) whether on same IP or not.
I would suggest you create unique content for all the domains individually. Alternatively, you may use a 301 redirect to direct traffic from the alternative domain (example2.org) to your preferred domain (example.com). This tells Google to always look for your content in one location, and is the best way to ensure that Google (and other search engines!) can crawl and index your site correctly.
More on it here:My Webpage
This post has been edited by C.Rebecca: Mar 12 2012, 05:45 AM