If there is already a well established website and somebody copies everything including content, then he is just inviting nothing but trouble. That was in case well established website. But if there are 2 websites, which newly launched. Say for example Website A launch 2 months ago with few content but no promotion and development work is done further. But website B launch after 2 months with same design and few duplicate content, but he develop (content) and promote the website as the time passes, then there is a high chance of going ahead in competition with website A coz I have seen this happened.
In case of duplicate sites, the age or usage of the website domain will determine its originality and the other will be given lesser priority by Google
i dont think google is as godlike as some people think here because i've seen two similar pages. one that is well established and the other which was scraping the other site and outputting the same content in a different template, was right below the original's SERP, and not to mention slightly lower but very similar level of traffic.
for example getafreelancer.com and look at this site: http://pro-freelance.com i googled for a project i posted before in google, and getafreelancer showed up and right below it pro-freelance.com