.com AND .co.uk.

[ojwilliams8]

Many of the massive sites (like Amazon) are using both .com and .co.uk. For smaller sites, is this a good way to rank highly on Google.com and .co.uk? Is there a way to do this without duplicating content or diluting link juice?

[TommyTan]

For Amazon and other massive sites, they have both .com and .co.uk is because they are targeting different people from different locations with tthe site.  The .com domain is targeting people in the US and .co.uk is for people in UK.  Therefore, when people search for Amazon, the .com domain will be the one that appears in search engine while the .co.uk domain will appear in the results for people in UK searching for Amazon.

If you want to rank better in Google.com, then you can create a .com domain and for .co.uk you can create a new website with the .uk ccTLD or create a subfolder within your .com domain geotargeting UK.