GWT - International Targeting

[twitime]

By selecting a country in the Country Targeting section of GWT what effect does this have?

For example if I select UK will this boost rankings on google.co.uk and decrease them on google.com etc?

If we are based in the UK but our customer base is worldwide should we not select anything?

[SEO-Buzz]

By providing Google Webmasters Tools with your international targeting information, you are helping Google decide if your website should appear and how it should appear (in local results) in a location. It only affects results for geographically related queries in which a user limits the scope of a search to a certain country.  It will not affect appearance in search results that are not geographically bounded. Hope that helps.