Flickr has rolled out a new feature called GeoFences, which basically allows you to define areas on a map where your geotagging of photos will not show up. You can set it up from the
Geo Preferences page in your account.

Note though, this feature isn't perfect yet, Thomas Hawk notes that it has a huge security flaw in that anyone can download the original image and view the geolocation data from the EXIF data.