By having a landing page that isn't just a giant map. You need to explain what your site does. As it is, I suspect most of your visitors will arrive and depart almost immediately.
We do have a bounce rate of about 40%, which is something we're trying to manage. I think part of that is not knowing what to do on the site, and part of it is because the site is really slow (until tomorrow when we launch the new version).
We're thinking about switching from a giant map home page to having the "Geo News" (in the main menu) as our home page, once the news page is polished.
We'll do that eventually... it's just another feature filed in our bug tracker. It's not clear how valuable that is though, particularly on a US level.
The first goal for personal geo-location will be to show foreign visitors a world map.
