Your profile most likely has this phrase:
top X% this week/month/quarter/year
Would be nice if you could enable an option to
compete regionally. For example:
top X% this week/month/quarter/year in Canada
top X% this week/month/quarter/year in Wisconsin
I read on the net that SO can sometimes help you get hired. This feature may be able to increase your chances, because most employers only compare you with your competitors in the current job market. They don't care if there is a better guy in another state or country, they need someone right here, right now. If you are able to show that out of 100 guys, you are number 1 in, let's say, New York (and you are applying for a position in NY), I think it's a better chance than saying you are top 100 out of 10000 (without any regional binding), even though both facts translate into the same top 1% standing.
Regarding implementation, I suggest going down to country level and to state/province level, where available (for example, US/Canada). Also don't make it public by default, so only if you go to your profile, you will see how you compete regionally. If you like the numbers, you may choose to publish them.