We are all aware about the search engines like Google, Yahoo, Yantex, Bing, etc. will blacklist the sites (In case of websites), if duplicate content has been identified. While we are establishing the business to world, we may require to implement country specific domains and multilingual support in the websites. Nobody will take care of how the search engines consider all those pages.
These search engines also provide different methods to notify them, about the duplicate content. To handle the duplication of contents in multi-domain sites 'rel=canonical' can be used. Google has put forward rel="alternate" hreflang="x" to handle multiple languages in the site.
Add links of other language versions in the header of every pages in the site.
Eg : "<link rel="alternate" hreflang="es" href="http://example.com/es" />"
In Drupal the efficient way to implement a multilingual site is using entity translation module
Implementing hreflang with entity translation module is very easy. Install the 'hreflang' module which implements hook_page_build() and hook_language_switch_links_alter().
Hope this will help. Have a try!