I've found plenty of postings regarding ways of avoiding dupe content penalties when operating the same website under different domains, such as .co.uk for the UK market & .com for the US.
Essentially it seems to boil down to 1 of 2 approaches:
1) Select one you want Google to index and ring fence the other domains so they don't get indexed.
2) Ensure there are sufficient differences between the sites operating under different domains so, while they use the same content, Google's dupe filters don't kick in. Generally recommendations are change title tags, headings, nav links, directory & page file names plus host sites separately to ensure they have different IP C block addresses.
The problem I see with Option 1 is if you operate in a number of different countries you will limit your ability to be found by searchers using the "Only pages from your country" results. Google provides this filter if you use google.co.uk, google.com.au, etc. My experience is that many users seach using this so you need to ensure your site can be found this way.
As I understand it the filter works by presenting sites that either have a country's TLD, (eg co.uk), or if the site has a non-country specific TLD (eg .com) Google will show it in the filtered results if the host IP address is from that country. Based on this, if you have a site targeting both the US & UK markets the approach would be ring-fence the .co.uk domain from search engines and use the .com but host it in the UK. That way people in UK doing UK only searches in Google will find the site despite it being a .com.
However Option 1 won't work if your site needs to be found in the local searches of more than 1 country. eg your site targets UK, Australia and New Zealand.
Are there any other approaches that can be used in this situation instead of option 2?
I hope it's clear I'm looking at ways of getting legitimate mirror sites for different countries included in local search results, rather than the old spammers trick of dominating search results using duplicated sites.