I don't know how global consistency is actually useful, but I can easily think of ways it is less convenient.

For example, DST starts and ends on different dates in the UK and the US. Which dates should google return when someone from either country searches for just "DST end date?" Someone lives in Orange County and searches for "Orange County Sheriffs," which one of the eight Orange Counties should google return?

These are both examples where a localized — not even customized, just localized based on IP addresses — search results will easily help reduce headaches.

I wouldn't mind that one. That a man in the US and a woman in Japan would get different results for a search for "sushi restaurant" is perfectly reasonable (even if the woman in Japan was searching in English).

It's when two people in the same neighborhood got different results for the same search that I said "wait a minute, they're personalizing search results now for ad-targeting purposes" and ditched them. The potential for them to deliberately hide things from you was too great.