You can search by city by using a regular expression in the filter box (ex: nyc|new york).
Or possibly a 3-pane display (if desired).. Pick the Year/month, then the city, then see all the people in that city. Or similarly, Year/month, then the company (sorted), then the post.
I was also thinking the same exact thing when I was reading the post today. I guess HN readers think alike!