There is a 150 cache limitation. When there are more than the limit in an area, it will randomly display 150 caches.
The geocache browser is a KML file, the default file format for Google Earth. To start using the KML, go to your "My Account" page on geocaching.com. You should see the Google Earth badge.
Click on the badge.
Save the KML file to your desktop. Now open Google Earth.
From the File Menu click File | Open and find on your desktop "GeocachingNetworkKML.kml".
You'll notice that the file has been added to your Temporary Places on the left and you should see results on the map screen.
To keep the KML file next time you open Google Earth, you'll need to move it from the Temporary Places to My Places.
Simply Right-Click the KML file and select Save to My Places.
Now you can zoom in, select a geocache and view the cache page using the web browser built-in Google Earth.