I created this account, so everybody can see what I'm talking about.
http://la.matchmaker.com/who?sort=k login/pass: guy922/titanic
This is their Who's onlone page. The right column shows the distance from L.A. zipcode 90004 (I entered at the registration) to all of the people who are currently online.
(I guess DC dating service software wasn't successful because they didn't have that feature)
Anyway, if anybody have any ideas about how it's done please share it with me.