Google started building a firm base of her algorithm based on a certain idea in mind - people like localized results. People searching for pizza would prefer pizza delivery services in their area, and if we could improve that and show them exactly where it is, we will earn a whole lot more and improve our search results.
Based upon that concept the organic search results changed dramatically (some during mayday update). Google maps were added, as well as Google's places and more.
It's a pretty simple concept. In first glance, it seemed perfectly logical to me. Then I started looking for queries in English (because local results usually SUCK) in google.com, with my non American IP. The average, non experienced, user would not know how results change when your IP-detected Google still has results according to his automatically picked language.
These results are absolute spam. Strong English sites are mere shadows of their original local, site. Some sites build by locals, hosted on the a local host, rank despite their low quality content. Also people who has mediocre English sites and linked to it from their network of local sites do well. Who will remain out? all the relevant results of course.
Mr Cutts, for your attention.