As Will Cole said back in January, this is a planned feature, and believe me, it's one we talk about often, and one I have a personal interest in improving.
I had been thinking for a couple years about moving from Boise, Idaho to New York City. When I decided to try to make that happen last spring, I joined Careers and marked myself as willing to relocate to NYC, only to be disappointed by the ad algorithm always suggesting to me jobs by the same company in Boise who, while they may be a great company, I had no interest in applying to.
However, I did end up finding a job on Careers (in more ways than one, you might say), and one of my first suggestions/complaints was exactly what you are requesting.
So why hasn't it been done yet?
Without going into too much detail, our existing ad infrastructure has a lot of limitations when it comes to customization. We could improve the results for some people, but it might come at the cost of others. We already know that current geography is relevant to a large number of users regardless of their willingness to relocate, so it's the best compromise we current have.
Good news, everyone!
There is a project in the works to solve this problem, headed by the same person who wrote the geography blog post. Even better, parts of it might become open source! I can't give you even the vaguest timeline estimate, but I wanted to let you know when I tag this as
status-planned that it really is planned, even if you don't see immediate progress. We see this project as vital to our business, and it won't be going away or forgotten about.