it shows that google really does things way before we think. This is an old thread and now we have webmaster tools and geo targetting. Google now offers different results to every user. Probably not just due to country, but IP address and your past habits. I also think that high in the serps sites for any given keyword can rotate or change back and forth daily so really we have no longer a static serp but a constantly moving one.
I have noticed also that if you can rank in top 10 in Google.com then you will rank even higher in any other Google per country servers