Google Social search results – but only on Google.com for now?

Last week, Google announced a series of updates to their social search feature that highlights links that have in some sense been “shared” by members of your social circle (An update to Google Social Search):

I’ve been wondering why I couldn’t see the social results whenever I ran a search, but today found out why: they only appear in results pages from google.com

… and I typically use google.co.uk….