It's certainly a nice addition to the built-in distance finder (which often says that people are near me when they are actually across a large body of water).
There doesn't seem to be any way to hide the map, other than turning off the script and reloading the page. It would be best if it only popped up when you need it (hovering over or clicking on a location), and was hidden and not accessing google otherwise.
It doesn't seem to work on profile pages, probably because OkCupid keeps updating their site.
It might be good to write the distance information right on the page instead of in a tooltip.
It might be best to require clicking on a location to calculate and display the map rather than hovering over it.